To determine risk factors for non-use of condoms when engaging in sexual intercourse among high-risk population groups for acquiring HIV/STIs. We collected the data obtained by interviews in the period from 2005 to 2011 in the Voluntary Counseling and Testing Center for HIV/AIDS at the Institute of Public Health of Zadar County. Four hundred ninety four respondents were divided into risk and control groups. The majority of the respondents in our population does not consistently use condoms, in the risk group as much as 89.9%, and in the control group 65.7% of them (p< 0.001). Persons consuming alcohol when having sexual relations use condoms about 5x less often compared to those not consuming alcohol at all (OR=5.00; CI=1.69-14.29). There are significant differences among women and men in the risk group regarding reasons for non-use of condoms. The main reason with women is "I trust mypartners" 33.7% while men "do not like having sex with condoms, 53.6% of them (p < 0.001). The main risk factors for non-use of condoms are alcohol consumption at sexual relations, non-use of condoms in a casual relationship. Having in mind the non-use of condoms among populations of high-risk groups of acquiring HIV there are significant differences among genders.