We sought to determine whether the influence of two factors known to influence smoking initiation (parental smoking and lower academic attainment) vary by age of smoking initiation and to develop profiles of smokers based on their age of smoking initiation. We analyzed data on demographic and smoking characteristics from 1,447 former and current cancer-free smokers, born between 1912 and 1975, who served as controls in an ongoing lung cancer case-control study, and who reported initiating smoking before their 31st birthday. Parental smoking exerted a significant influence among the youngest initiators (<15 years) only, and the magnitude of the influence from academic attainment decreased with increasing age of initiation. The youngest initiators were less likely to have quit, had smoked for more years, and reported higher levels of nicotine dependence than the oldest initiators. Our results underscore the continued need to target smoking prevention messages toward individuals younger than 15 years. Because the influence of parental smoking was pronounced among the youngest initiators, family smoking dynamics must be addressed to develop effective prevention programs tailored to this at-risk age group.