We compared the final adult height (FH) of patients with classic constitutional delay of growth and puberty with their target height (TH) and with the height prediction by the Bayley-Pinneau method (BP). 20 patients and their parents were included in our study: 6 females (mean age 19.1 years) and 14 males (mean age 20.6 years). No significant difference could be detected between TH, FH and BP prognosis. This is in contrast to recent studies using height data partly obtained by self-estimation. We measured our patients and their parents ourselves and were accurately able to calculate their genetically determined TH. This proceeding could explain our results. Our study shows that adolescents with true constitutional delay do not need treatment and that height prediction seems to be accurate.