Background: Area-level socioeconomic conditions are associated with epidemic rates of viral hepatitis and HIV amongst urban injection drug users (IDUs), but whether specific socioeconomic markers are uniformly related to IDU outcomes across different urban environments is unclear. We evaluated whether injection behaviour is differentially related to neighbourhood socioeconomic characteristics for IDUs in inner city vs. surrounding urban areas. Methods: The study population was 468 active IDUs on the Island of Montréal. Neighbourhoods were represented as 500 m radius buffers around individual IDU dwelling places. High-risk injection behaviour (HRIB) was defined dichotomously. Relations between neighbourhood socioeconomic disadvantage (percentage households below low-income cutoff), neighbourhood educational attainment (percentage adults with university degree), and HRIB were assessed using multivariate logistic regression. Stratified analyses were conducted for inner city IDUs (n = 219), and those in surrounding areas (n = 249). Results: Similar proportions of IDUs in inner city and surrounding areas reported HRIB. Neighbourhood socioeconomic characteristics were not associated with HRIB for IDUs in surrounding areas. For inner city IDUs, those in socioeconomically disadvantaged neighbourhoods were more likely to practice HRIB (OR 4.34; 95% CI 1.15-16.35). Conversely, inner city IDUs residing in lower educational attainment neighbourhoods had a lower odds of HRIB (OR 0.41; 95% CI 0.21-0.80). Conclusion: HRIB did not vary according to urban environment but for inner-city IDUs was differentially related to socioeconomic markers. Associations between HRIB and neighbourhood socioeconomic disadvantage and lower educational attainment, positive and negative, respectively, indicate that adverse socioeconomic circumstances are not related to a uniformly greater likelihood of HRIB.