Aim: The objective of this study was to assess the validity of a mobility questionnaire (MobQues) that was developed to measure parent-reported mobility limitations in children with cerebral palsy (CP). Method: The parents of 439 children with CP (256 males and 183 females; age range 2-18y; Gross Motor Function Classification System [GMFCS] levels I-IV) completed the mobility questionnaire (MobQues). To assess content validity, we linked all meaningful concepts of the MobQues items to the International Classification of Functioning, Disability and Health (ICF). To assess construct validity, we compared the total scores of the two versions of the MobQues (MobQues47 and MobQues28) according to GMFCS level, and determined Pearson's correlation coefficient ("r") with the Gross Motor Function Measure-66 (GMFM-66). Results: Content validity was demonstrated by the fact that 46 of the 47 MobQues items were linked to categories in the "Mobility" chapter of the ICF. Construct validity was demonstrated by the finding that MobQues scores decreased with increasing GMFCS levels (p less than 0.001). In a subgroup of 162 children, positive correlations were found between total scores and the GMFM-66 (MobQues47, r=0.75; MobQues28, r=0.67, p less than 0.001). Interpretation: The results of this study provide evidence supporting the content and construct validity of the MobQues as a measure of mobility limitation in children with CP.