This randomized controlled trial aimed to examine the effectiveness of a smoking cessation intervention using a risk communication approach. A total of 528 smoking cancer patients were randomly allocated either into an intervention group (n = 268) to receive brief advice based on risk communication by a nurse counselor or a control group (n = 260) to receive standard care. Subjects in both groups received a smoking cessation booklet. Patient follow-ups were at 1 week and at 1, 3, 6, 9 and 12 months. No significant differences were found in self-reported point-prevalence 7-day abstinence between the intervention and control groups at 6 months (15.7% vs 16.5%; OR 0.94, 95% CI 0.59-1.50). The rate of at least 50% self-reported reduction of smoking at 6 months, was higher in the intervention group than in the control group (16.8% vs 12.3%; OR 1.43, 95% CI 0.88-2.35). The biochemically validated quit rate at the 6-month follow-up was higher in the intervention group than in the control group (5.2% vs 3.8%; OR 1.38, 95% CI 0.60-3.16). These data suggest that advice based on risk communication was not effective for quitting but improved the rate of smoking reduction among smoking cancer patients.