Obesity is a risk factor for numerous health problems. Behavior therapy is important for obesity treatment. The aim of the present study was to identify the parameters that are associated with successful weight reduction. A database of 123 subjects who underwent weight reduction programs at the Center for Health Promotion, Samsung Medical Center from June 2001 through November 2004 was retrospectively analyzed. The goal of the program was to reduce the body weight by more than 5% during the follow-up period. The study population was divided into 2 categories (the success group and the failure group) based on the outcome of weight reduction. We analyzed the demographic, laboratory and clinical parameters to determine the predictors of successful weight reduction. The prevalence of success group was 36.6% (45/123). Significant correlations for successful weight reduction were found for the follow up period and the frequency of medical visits. Our results suggest that strong motivation was the most important factor for successful weight reduction.