The present work tests the applicability and validity of the CAFAS, an instrument for assessing functional impairment, in the Spanish population. The sample included 441 psychiatric outpatients from 8 to 17 years old and their parents, and a pediatrie group of 74 outpatients. Different instruments for assessing functional impairment, psychopathology, and other related variables were used. Interrater reliability ranged from moderate to very good. Weak-to-moderate agreement between CAFAS scores based on information from parents and children was obtained. Correlations with other measures of impairment and functioning were moderate. CAFAS scores differentiated significantly between children with and without psychopathology. These results permit the use of the instrument for studies on psychopathology and functional impairment, and for planning intervention and mental health services. © 2006 International Association for Applied Psychology.