Background: Generally, non-smokers have healthier lifestyles compared to smokers. Typical foods eaten more by nonsmokers are fruits and vegetables, whereas smokers eat more meat and fat and DRINK more alcoholic beverages. We aimed to compare nutritional knowledge, attitude and practice (KAP) of smokers participating in smoking cessation clinics with their non-smoker family members.Materials and Methods: Two hundred twenty-six smokers and 260 non-smokers aged 18 years and over were compared in a cross-sectional study. A Likert type KAP questionnaire including 36 items was used. Knowledge and attitude scores were compared between smokers and non-smokers using the Mann-Whitney test. Practice patterns were compared by the Chi-square test. Differences were significant at p =0.05.Results: The mean age of male smokers and non-smokers were 38.5±11 and 33.5±14 years respectively and in women these rates were 42±10.4 and 31.3±15 yrs. respectively (p<0.0001). In males, the mean percentage of knowledge in nonsmokers was higher than smokers (2.41 vs. 1.85) and the average score of attitude in smokers was less than that of nonsmokers (37.5 vs. 37.9; the differences were not significant). Sixty (26.5%) smokers and 93 (35.8%) non-smokers reported having regular physical activity (p=0.005). In women, the mean percentage of knowledge in non-smokers was higher than smokers (3.37 and 2.93 respectively; the difference was not significant). Attitude score of female non-smokers was higher than smokers (40.3 vs. 37.1; p=0.001). Among female non-smokers, 68 (46.9%) reported daily meat consumption; this rate for female smokers was 41 (56.2%; p=0.001). Female non-smokers consumed daily breakfast more than female smokers (107, 73.8% vs. 35, 47.9%; p=0.001).Conclusion: Our data showed a significant difference in nutritional KAP between smokers and non-smokers.