Abstract: Objective To examine the prevalence and influencing factors of internet addiction and the association of impulsive choice with the addiction among students in a medical university in Liaoning province.Methods A total of 2213 students were selected with stratified cluster sampling from a medical university and surveyed with a questionnaire about general information and internet use and Barratt Impulsiveness Seale-Chinese Version(BIS-11) between February 2014 and July 2015.Results The overall prevalence of internet addiction was 18.6%(412/2213) based on the criteria proposed by China Center for Disease Control and Prevention.The female students reported more internet use for shopping, listening to music, and watching movies, while the male students reported more internet use for playing games.Of the students, 59.6% had less than 3 hours of internet use per day and only 6.4%had more than 6 hours of internet use per day; the daily internet use time was significantly different among the students of different gender, grade, and whether being a medical student(all P<0.01).The prevalence of internet addiction differed significantly by gender and years of study in the university among the students(χ²=10.712, P=0.001), with the prevalence rate of 22.7%(159/701) for the males, 16.7%(253/1512) for the females, 20.9%(93/445) for the freshmen, 19.9%(111/560) for the sophomores, 18.9%(93/491) for the juniors, 17.7%(69/392) for the students of grade four, and 14.2%(46/325) for the students of grade five, respectively.Multivariate analysis showed that the main influencing factors of internet addiction among the students were female gender(odds ratio OR=1.460), being a freshman(OR=2.284-2.724 compared to the students of other grades), majoring in medicine(OR=3.915), location of hometown(OR=0.490 for township and OR=2.052 for rural area compared to urban area), family pattern(OR=0.455 for single-parent family and OR=2.434 for other family patterns compared to two-parent family), attitude of parents(OR=1.303 for negative attitude and OR=1.439 for neutral attitude compared to positive attitude), and with introvert personality(OR=1.389).Internet addiction was positively correlated with impulsive choice and its three dimensions significantly among the students(all P<0.05).Conclusion Internet addiction is influenced by gender, grade, majoring, location of hometown, family pattern, parental attitude, communication with parents, and personality and positively correlates with impulsive choice among students in medical college.