The relationship between personality characteristics and spontaneous modification of smoking habits was assessed in 164 patients after their first myocardial infarction (MI). Smoking habits before the MI were investigated in retrospect and 5 months later. Smoking appeared to have decreased significantly. Persistent smokers could be differentiated from nonsmokers and exsmokers by a significantly high level of state-anxiety and depression. Young persistent smokers had a high level of depression; elderly persistent smokers were highly anxious and had a low level of somatization. The relationship between smoking behaviour modification and personality characteristics is discussed in association with intervention programmes.