Aims: The purpose of this study was to investigate the effect of a 12-week strength training, and 3 months of detraining on physical fitness, body composition, and quality of life. Methods: Twenty women underwent assessments pre-and post-training, and after cessation of training. The measurements included waist-to-hip ratio, muscle mass, fat mass, leg press and seated row strength, functional fitness (SFT), and quality of life physical component score (PCS) and mental component score (MCS). Results: Significant interaction (p < 0.01) was found in all tests except for the PCS. The subjects in the EX group significantly improved in all tests (p < 0.01) from pre-to post-training. However, during the detraining, strength, SFT, and MSC significantly worsened from post-to detraining (p < 0.01). Body composition, except for muscle mass, remained unchanged. Conclusions: It seems that body composition persists for prolonged times, compared to performance characteristics. However, the results should be interpreted with caution, because improvements in body composition had small effects (g ¼ $0.20-0.32).