BACKGROUND The study assessed changes in functional performance of children with cerebral palsy (CP), immediately following treatment and 2 months later, in addition to investigating the relationship between therapy effect and sex, age, or comorbidities. MATERIAL AND METHODS Functional performance of 32 children with spastic diplegia CP, aged 9-16 years, was assessed for: 1) manual function (Box and Block test), motor capacities (Gross Motor Function Measure), sensory capacities (Finger Identification [FI] and Localisation of Tactile Stimuli test [LTC]), and 2) activity and participation, ie, independence in essential and more complex daily activities (Barthel Index; Paediatric Evaluation of Disability Inventory). Measurements were conducted before the start (Month 0), immediately after 6-month rehabilitation program (Month 6), and following a 2-month period with no therapy, ie, 8 months after baseline measurement (Month 8). RESULTS Comparison of Month 0 and Month 6 scores showed significant differences (P<0.001) in all measures. However, Month 8 scores were significantly worse in all the measures, except for sensory capacities assessed using FI and LTC (P<0.001). CONCLUSIONS Functional performance of children with CP was positively affected by 6-month therapy, but 2 months later these effects significantly deteriorated, except for the sensory capacities. This suggests that therapy focusing on functional performance should be included as a permanent component of rehabilitation programs. These findings may be important for clinical practice as they show that therapy of children with CP should be continuous and systematic, and this should be taken into account by those designing therapeutic programs.