The study examines the validity of a body image questionnaire (FKB-20) assessing body image disturbances in a clinical sample (n = 405 outpatients of a psychosomatic clinic) and two non-clinical samples (n = 141 medical students and n = 208 sports students). The criterion group was constituted by 98 patients of the clinical sample with diagnosed body image disturbances (anorexia, transsexualism, hypochondriac symptoms). The validity coefficients were 0.56-0.65. The sensitivity of the questionnaire was 82-90%, the specificity 90-97%, and the total mistake rate was 8-10%. The FKB-20 proves to have good validity and can be used for the diagnosis of body image disturbances.
