BACKGROUND While the prevalence of young female smokers is rising among the Hong Kong Chinese population, data on their smoking pattern during pregnancy are limited. OBJECTIVE To investigate the smoking habit of Hong Kong Chinese women and their partners during pregnancy. METHODS Postal questionnaires were sent to 479 couples to explore their smoking patterns during pregnancy at one to two years after the index delivery. RESULTS Questionnaires were completed by 247 subjects. Among 117 women who were ever-smokers, 26% had stopped smoking before the index pregnancy, while 60% stopped and 14% reduced smoking during the pregnancy. Most women stopped smoking in the first trimester (93%) and prior to the first antenatal visit (79%). Those who used to smoke fewer cigarettes before pregnancy were more likely to stop smoking during pregnancy but women with a history of recreational drug use were more likely to continue smoking during pregnancy. The post-partum smoking relapse rate was 59% in women who had stopped smoking before or during their pregnancy. Only 2.6% of the partners who were ever-smokers stopped smoking before the pregnancy while smoking habits remained unchanged in 52%. CONCLUSIONS Approximately one-fifth of an unselected sample of Hong Kong mothers had a history of smoking prior to pregnancy. Pregnancy is an opportune time to implement smoking intervention programs for female smokers and their partners with an emphasis on the maintenance of post-partum smoking abstinence.