Formation and expansion of informal habitations with undesirable physical, economic and social characteristics are among the consequences of urbanization growth in the city of Zanjan. «Biseam» informal habitation is among the big informal residential regions in the city of Zanjan, which is the outcome of anomalous and uncontrolled immigrations of peasants to cities. The region is faced with many problems and insufficiencies with respect to its physical aspects. The entire physical characteristics of the region along with demographical and social characteristics dominating the region have led it to become the focal venue for a considerable level of crimes in Zanjan city. The present research aims at surveying the impact of «Biseam» informal residential region in formation of delinquency patterns in the city of Zanjan and expressing the factors effectively contributing to delinquency in the region. The research method, which is of analytical-comparative type used medium centre and oval criteria deviation tests, clustering test, nearest neighbor indices, and Kernel density estimation for analyzing delinquency patterns. The statistical community of the present research includes all the drugs trafficking related crimes occurred in a period of one year in city of Zanjan.The findings of the research indicate that «Biseam» informal habitation is the region, which is prone to drugs trafficking crime. The relative population density in «Biseam» is higher than that of other areas in the city of Zanjan, so is the unemployment rate compared with other areas in the city of Zanjan. On the other hand, excessive numbers of houses, lack of the required urban facilities such as parks, cultural centers, sports facilities and police stations, which have made formal surveillance over the activities of the inhabitants of the area difficult, have been so effective in the geographical distribution, type and level of crime, and formation of delinquency patters in the area.Therefore, it seems that organizing and allocating per capita facilities, equipment and services, establishing healthy recreational and leisure centers, widening pavement networks, determining suitable places for settlement of police forces and improving the physical conditions of houses in the region can reduce the vulnerability of the region against crime occurrence in the region.