Cerebral palsy (CP) is the most common cause of permanent neurological disabilities in children. Many children require long-term daily physiotherapy (PT), and videogaming is a promising tool to increase motivation in rehabilitation. The short- and medium-term effects of an intervention with rehabilitation specific videogames were evaluated on individually defined therapy goals, gross motor function, and motivation. Thirty-two children with bilateral spastic CP, Gross Motor Function Classification level III-IV, and 6-15 years were randomized into an intervention group (regular PT and gaming) or a control group (regular PT), followed by a crossover. The effects of both training periods (each 12 weeks) were compared using the Goal Attainment Scale (GAS), Trunk Control Measurement Scale (TCMS), Pediatric Balance Scale (PBS), Gross Motor Function Measure-88 (GMFM-88), and Dimensions of Mastery Motivation Questionnaire (DMQ). After 3 months follow-up, children were retested using the GMFM, TCMS, and PBS. The GAS change scores were significantly higher after the intervention compared to the control period (8.5 and 2.4, P < 0.001). The change scores for standing exercises (3.85 and 0.22, P = 0.04) and dynamic sitting balance (5.9 and -1.7, P < 0.001) were also significantly higher. After 3 months follow-up the results did not persist. A combined approach of regular PT and rehabilitation specific gaming showed significant effects on individually defined therapy goals, dynamic sitting balance, and standing exercises. However, the lack of persistent effect indicates that continuous individual goal-oriented PT with the addition of gaming is needed.