The General Health Questionnaire (GHQ) is a self-report questionnaire designed to identify psychological distress. Psychometric properties of two versions of GHQ-12 and GHQ-20 were assessed in a large population-based sample of Finnish twins, ages 22 to 27 (n= 4580). Participants were randomized into two subgroups, namely Twin1 (n= 2294) and Twin2 (n= 2286). The GHQ-12 data were assessed using Confirmatory Factor Analysis (CFA). The factor structure of the GHQ-20 was first assessed with Exploratory Factor Analysis (EFA) in the Twin1 dataset, and the results obtained were then subjected to CFA in Twin1 and Twin2 datasets. The CFA of the GHQ-12 indicated that the best fit and the simplest solution were provided by the three-factor solution in both subpopulations. Analyses of the GHQ-20 suggested that the four-factor structure was superior to the three-factor model. This result is also theoretically justifiable. Compared to the 12-item version, GHQ-20 provides additional fourth factor of anhedonia, suggesting some discriminative power.