This article shows the results of a socially significant research, the relevance of which is constantly growing in current conditions, due to the impending global crisis. Research objectives are to develop theoretical knowledge in sphere of quality ecological assessment of the urbanized territories and identification of opportunities for their practical use in certain regions. Authors have systemized factors that affect on the quality of urban environment and identified main approaches, which are used in implementing of the quality ecological assessment of the urbanized territories’ environment. Results of ecological and hygienic assessment of air quality of Irkutsk Region’s (Russia) cities have been introduced as a part of the author’s methodology. Main sources of pollution and their impact on atmospheric pollutant emissions have been identified. Urban areas with high level of air pollution have been revealed. Based on the findings, set of measures has been proposed to restore ecological balance in Irkutsk region, the implementation of which will improve the environmental conditions of atmospheric air as one of the criteria of quality assessment of urban territories. Methods of systemic and comparative analysis, expert opinions and social polls as well as ecological monitoring of the environment have been used during the research.