Effects of a transdermal nicotine substitution on psychological smoking cessation were investigated in a double-blind prospective study. 131 smokers have been randomly assigned to three treatment conditions: All smokers underwent nine weeks of self-controlled smoking cessation. During 6 weeks one group was additionally treated with nicotine patches continuously releasing nicotine through the skin into the blood circuit. The second group received placebo patches; while the third group was treated with behavioral training alone. Treatment effects were measured by daily cigarette consumption. Follow-up investigations were performed 3, 6 and 12 months after therapy. Nicotine-treated subjects reached significantly higher abstinence rates during and at the end of treatment as well as during the follow-up period, than both placebo- and control-subjects. No severe side effects of plasters have been reported. The results thus indicate good therapeutic effectiveness of transdermal nicotine substitution.