The COSMIN guideline provides a ten-step methodology for conducting systematic reviews of patient-reported outcome measures (PROMs). The guideline aims to improve the quality of systematic reviews by combining the methodological quality of studies on measurement properties with the quality of the PROM itself. The process includes preparing and performing a literature search, evaluating the quality of eligible studies, assessing measurement properties, and formulating recommendations. The ten steps are divided into three parts: A (literature search and selection), B (evaluation of measurement properties), and C (selection of PROMs). The guideline emphasizes the importance of content validity, internal structure, and other measurement properties in assessing PROMs. It also includes methods for evaluating the interpretability and feasibility of PROMs. The guideline is based on expert opinions and existing guidelines, and it provides detailed information on how to conduct systematic reviews of PROMs, including the use of search filters and the GRADE approach for grading the quality of evidence. The guideline supports evidence-based selection of PROMs for research and clinical practice.The COSMIN guideline provides a ten-step methodology for conducting systematic reviews of patient-reported outcome measures (PROMs). The guideline aims to improve the quality of systematic reviews by combining the methodological quality of studies on measurement properties with the quality of the PROM itself. The process includes preparing and performing a literature search, evaluating the quality of eligible studies, assessing measurement properties, and formulating recommendations. The ten steps are divided into three parts: A (literature search and selection), B (evaluation of measurement properties), and C (selection of PROMs). The guideline emphasizes the importance of content validity, internal structure, and other measurement properties in assessing PROMs. It also includes methods for evaluating the interpretability and feasibility of PROMs. The guideline is based on expert opinions and existing guidelines, and it provides detailed information on how to conduct systematic reviews of PROMs, including the use of search filters and the GRADE approach for grading the quality of evidence. The guideline supports evidence-based selection of PROMs for research and clinical practice.