The overall aim was to assess the reliability and accomplish a limited validation of the Pediatric Quality of Life Inventory 3.0 Cardiac Module Scales (PedsQL 3.0), Swedish version, in a sample of Swedish children diagnosed with congenital heart defects (CHD). A secondary aim was to assess whether the children's health-related quality of life (HRQOL) was affected by gender, age, severity of the CHD, surgical intervention and whether the child self-report and parent proxy-report were consistent. A total of 126 families at The Queen Silvia Children's Hospital, Sahlgrenska University Hospital, Gothenburg, participated in the study. The PedsQL Inventory 4.0 Generic Core Scales (PedsQL 4.0) and the PedsQL 3.0 were administered to 94 children (aged 5-18 years) with CHD and 126 parents (of children with CHD aged 2-18 years). The results showed that the internal consistency of the PedsQL 3.0 reached or exceeded Cronbach's alpha values of 0.70 for both child self-report and parent proxy-report. The PedsQL 4.0 and PedsQL 3.0 were highly correlated (r ¼ 0.78 for parents and r ¼ 0.79 for children), indicating convergent validity. Age group 5-7 years had the lowest estimated HRQOL in comparison with the age group 8-12 years and 13-18 years. The group of children with severe cardiac disease generally reported significantly lower HRQOL as compared with the mild and moderate groups ( p , 0.05). Children who had undergone cardiac surgery reported lower cardiac-specific HRQOL than children who were not surgically treated ( p , 0.05). In conclusion, the PedsQL 3.0, Cardiac Module, reached acceptable a-values and can be a useful tool in clinical practice and in research.