This prospective study examined the relationships between impulsivity, smoking and alcohol use in a large non-clinical sample of 601 men and 4832 women working in 12 Finnish hospitals. Data on impulsivity, smoking and alcohol consumption were collected by two questionnaires with a two-year interval. At baseline, impulsivity was associated with smoking and alcohol use. After controlling for baseline smoking, impulsivity predicted increased number of cigarettes smoked per day in women (p=0.08), but not in men. After controlling for alcohol use at baseline, impulsivity predicted increased alcohol consumption similarly in both genders (p<0.01). Higher impulsivity was also associated with increased likelihood of taking up smoking or becoming a heavy drinker (p<0.05). This evidence suggests that impulsivity contributes to increasing health risk behaviours.