This study assessed the relationship between the smoking behavior of adolescents and the smoking status of their parents and friends among adolescents from six European countries. A longitudinal study collected data from 15 705 adolescents on their own smoking status, and that of their parents, best friend and friends in general. Cross-sectional regression analysis showed that adolescent smoking was most strongly associated with friends' smoking and best friend's smoking, explaining 38% of the variance in the total sample. Longitudinal regression analysis, however, showed that the beta coefficients of the smoking status of the best friend and friends in general were comparable to that of parental smoking. Parental smoking behavior was found to be as predictive of smoking onset after 1 year as friends' smoking status.