The Compulsive Internet Use Scale (CIUS): Some Psychometric Properties This study aimed to develop a short, easy-to-administer, psychometrically sound instrument to assess the severity of compulsive internet use (CIU). Based on literature, criteria for CIU were determined, and the internal consistency and convergent validity of these criteria were evaluated. The CIUS, consisting of 14 items rated on a 5-point Likert scale, was tested in three representative samples of heavy internet users. The instrument demonstrated good factorial stability, high internal consistency, and strong correlations with concurrent and criterion variables, indicating its validity. The CIUS is a reliable and valid tool for assessing the severity of CIU. The concept of CIU, sometimes referred to as internet addiction or pathological internet use, has been debated since the mid-1990s. While there is no consensus on a universal theoretical framework, the DSM-IV criteria for substance dependence and pathological gambling were used to develop the CIUS. The criteria for CIU include loss of control, preoccupation, conflict, coping, and lying about involvement. These criteria were derived from qualitative studies and literature on internet use. The CIUS was validated against the Online Cognition Scale (OCS), which measures pathological internet use. High correlations were found between the CIUS and the OCS subscales, indicating good concurrent validity. Additionally, the CIUS showed a positive correlation with time spent online, supporting its construct validity. The study confirmed that CIU is a significant issue, with some internet users becoming overly involved in internet use, leading to interference with personal wellbeing and causing or aggravating psychological, social, and work-related problems. The CIUS is a reliable and valid instrument for assessing the severity of CIU, making it a useful tool for further research and clinical applications.The Compulsive Internet Use Scale (CIUS): Some Psychometric Properties This study aimed to develop a short, easy-to-administer, psychometrically sound instrument to assess the severity of compulsive internet use (CIU). Based on literature, criteria for CIU were determined, and the internal consistency and convergent validity of these criteria were evaluated. The CIUS, consisting of 14 items rated on a 5-point Likert scale, was tested in three representative samples of heavy internet users. The instrument demonstrated good factorial stability, high internal consistency, and strong correlations with concurrent and criterion variables, indicating its validity. The CIUS is a reliable and valid tool for assessing the severity of CIU. The concept of CIU, sometimes referred to as internet addiction or pathological internet use, has been debated since the mid-1990s. While there is no consensus on a universal theoretical framework, the DSM-IV criteria for substance dependence and pathological gambling were used to develop the CIUS. The criteria for CIU include loss of control, preoccupation, conflict, coping, and lying about involvement. These criteria were derived from qualitative studies and literature on internet use. The CIUS was validated against the Online Cognition Scale (OCS), which measures pathological internet use. High correlations were found between the CIUS and the OCS subscales, indicating good concurrent validity. Additionally, the CIUS showed a positive correlation with time spent online, supporting its construct validity. The study confirmed that CIU is a significant issue, with some internet users becoming overly involved in internet use, leading to interference with personal wellbeing and causing or aggravating psychological, social, and work-related problems. The CIUS is a reliable and valid instrument for assessing the severity of CIU, making it a useful tool for further research and clinical applications.