This study investigated the relationship between function classification systems and the Pediatric Evaluation of Disability Inventory (PEDI) functional skills in children with cerebral palsy (CP). Two hundred and eleven children with CP participated in this study. The Korean-Gross Motor Function Classification System (K-GMFCS), Korean-Manual Ability Classification System (K-MACS), Korean-Communication Function Classification System (K-CFCS), and self-care, mobility, and social function domains of the Korean-Pediatric Evaluation of Disability Inventory (K-PEDI) functional skills were measured by physical therapists or occupational therapists. All of the function classification systems were significantly correlated with PEDI functional skills ($r_s$=-.549 to -.826) (p<.05). Especially, K-GMFCS, K-MACS, and K-CFCS were correlated significantly with mobility, self-care, and social function, respectively. Using stepwise multiple regression analysis, we established that K-GMFCS, K-MACS, and K-CFCS were predictors of self-care skills (74.3%) and mobility skills (79.5%) of the K-PEDI (p<.05). In addition, K-CFCS and K-MACS were predictors of social function (65.9%) of the K-PEDI (p<.05). The information gathered in this study using the levels measured in the function classification systems may be useful to clinicians for estimating the PEDI functional skills in children with CP.