Aim: The aim of this study was to examine the relationship between gross motor capacity and daily-life mobility in children with cerebral palsy (CP) and to explore the moderation of this relationship by the severity of CP. Method: Cross-sectional analysis in a cohort study with a clinic-based sample of children with CP (n=116; 76 males, 40 females; mean age 6y 3mo, SD 12mo, range 4y 8mo-7y 7mo) was performed. Gross motor capacity was assessed by the Gross Motor Function Measure (GMFM-66). Daily-life mobility was assessed using the Pediatric Evaluation of Disability Inventory (PEDI): Functional Skills Scale (FSS mobility) and Caregiver Assistance Scale (CAS mobility). Severity of CP was classified by the Gross Motor Function Classification System (48% level I, 17% level II, 15% level III, 8% level IV, 12% level V), type of motor impairment (85% spastic, 12% dyskinetic, 3% ataxic), and limb distribution (36% unilateral, 49% bilateral spastic). Results: Scores on the GMFM-66 explained 90% and 84% respectively, of the variance of scores on PEDI-FSS mobility and PEDI-CAS mobility. Limb distribution moderated the relationship between scores on the GMFM-66 and the PEDI-FSS mobility, revealing a weaker relationship in children with unilateral spastic CP (24% explained variance) than in children with bilateral spastic CP (91% explained variance). Interpretation: In children aged 4 to 7 years with unilateral spastic CP, dissociation between gross motor capacity and daily-life mobility can be observed, just as in typically developing peers. © The Authors. Journal compilation © Mac Keith Press 2009.