The assessment of mindfulness through self-report questionnaires is essential for understanding its relationship with psychological functioning, health, and well-being. While mindfulness is often measured using self-report tools, these questionnaires have reasonable psychometric properties and contribute significantly to understanding mindfulness and its effects. However, differences between Buddhist and psychological conceptions of mindfulness are inevitable and not necessarily problematic. Mindfulness is generally understood as a psychological capacity involving present-moment awareness, nonjudgment, and nonreactivity. These qualities are often described as the "what" and "how" of mindfulness. Several mindfulness questionnaires, such as the Mindful Attention Awareness Scale (MAAS), Five Facet Mindfulness Questionnaire (FFMQ), and the Kentucky Inventory of Mindfulness Skills (KIMS), have been developed to assess mindfulness. These tools have shown strong internal consistency, test-retest reliability, and factor structure. However, their psychometric properties vary, and some studies suggest that mindfulness questionnaires may not fully capture Buddhist conceptions of mindfulness. Mindfulness is often defined in psychological terms as a state of present-moment awareness with nonjudgmental and nonreactive attitudes. However, research indicates that nonjudgment and nonreactivity may not always be strongly related to present-moment awareness, especially in individuals without meditation experience. The development of mindfulness questionnaires has primarily relied on contemporary sources, leading to criticism for not adequately capturing Buddhist conceptions. Despite these challenges, mindfulness questionnaires have made important contributions to understanding mindfulness. They have shown that mindfulness training increases self-reported mindfulness skills, and that mindfulness-based interventions (MBIs) have therapeutic effects mediated by increases in self-reported mindfulness. However, further research is needed to clarify the conditions that lead to the acquisition of mindfulness skills and to examine the incremental validity of mindfulness measures over other constructs like neuroticism. Anomalous findings, such as higher scores on mindfulness questionnaires in binge drinkers, have led to important insights. These findings suggest that present-moment awareness can be unhelpful unless accompanied by a nonjudgmental, nonreactive stance. This highlights the importance of unidimensional subscales in assessing mindfulness. While self-report questionnaires have limitations, they remain a valuable tool for assessing mindfulness. Objective behavioral tasks, such as breath counting, can supplement self-report methods but may not fully capture the nonjudgmental, nonreactive stance essential to mindfulness. Overall, mindfulness questionnaires have made significant contributions to the understanding of mindfulness in psychological science, despite their limitations.The assessment of mindfulness through self-report questionnaires is essential for understanding its relationship with psychological functioning, health, and well-being. While mindfulness is often measured using self-report tools, these questionnaires have reasonable psychometric properties and contribute significantly to understanding mindfulness and its effects. However, differences between Buddhist and psychological conceptions of mindfulness are inevitable and not necessarily problematic. Mindfulness is generally understood as a psychological capacity involving present-moment awareness, nonjudgment, and nonreactivity. These qualities are often described as the "what" and "how" of mindfulness. Several mindfulness questionnaires, such as the Mindful Attention Awareness Scale (MAAS), Five Facet Mindfulness Questionnaire (FFMQ), and the Kentucky Inventory of Mindfulness Skills (KIMS), have been developed to assess mindfulness. These tools have shown strong internal consistency, test-retest reliability, and factor structure. However, their psychometric properties vary, and some studies suggest that mindfulness questionnaires may not fully capture Buddhist conceptions of mindfulness. Mindfulness is often defined in psychological terms as a state of present-moment awareness with nonjudgmental and nonreactive attitudes. However, research indicates that nonjudgment and nonreactivity may not always be strongly related to present-moment awareness, especially in individuals without meditation experience. The development of mindfulness questionnaires has primarily relied on contemporary sources, leading to criticism for not adequately capturing Buddhist conceptions. Despite these challenges, mindfulness questionnaires have made important contributions to understanding mindfulness. They have shown that mindfulness training increases self-reported mindfulness skills, and that mindfulness-based interventions (MBIs) have therapeutic effects mediated by increases in self-reported mindfulness. However, further research is needed to clarify the conditions that lead to the acquisition of mindfulness skills and to examine the incremental validity of mindfulness measures over other constructs like neuroticism. Anomalous findings, such as higher scores on mindfulness questionnaires in binge drinkers, have led to important insights. These findings suggest that present-moment awareness can be unhelpful unless accompanied by a nonjudgmental, nonreactive stance. This highlights the importance of unidimensional subscales in assessing mindfulness. While self-report questionnaires have limitations, they remain a valuable tool for assessing mindfulness. Objective behavioral tasks, such as breath counting, can supplement self-report methods but may not fully capture the nonjudgmental, nonreactive stance essential to mindfulness. Overall, mindfulness questionnaires have made significant contributions to the understanding of mindfulness in psychological science, despite their limitations.