Rapid urbanization and high population growth is the most prominent phenomena of therncontemporary world particularly in the developing countries. As the urbanization process of thernthird world countries is attributable with complex socio-economic and demographic adversitiesrnthere is a need to elicit the different aspects of the unhealthy urbanization. Mental health is one ofrnthe most pressing development issues particularly in association with rapid growth ofrnurbanization.rnAddis Ababa, the capital of Ethiopia is the third fast growing cities of the world in terms of physicalrnexpansion and demographic facts. These phenomena coupled with lack of institutional capacity inrnthe provisions of basic social services create several socio-economic calamities of which thernprominent one is the prevalence of mental health disorder and psychological distress. Therefore,rnthis cross-sectional survey was intended to analyze and describe the demographic and socioeconomicrndeterminants of mental health illness and psychological distress among adult residentsrnof the city.rnIn order to address this issue, the methods utilized were that three sub cities of the capital werernselected targeting the mental health clinics of their respective health centers. The interview wasrnconducted by psychiatric nurses for purposively selected patients (n=300) who were diagnosedrnfor mental health disorders. The collected demographic and socioeconomic data were entered inrnSPSS-20 window software and analyzed using descriptive and econometric methods. Therndichotomous variables of mental illness and relevant demographic and socioeconomic predictorsrnwere cross tabulated to measure association using chi-square tests at significant level 0.05.rnLogistic regression model was also utilized and their odd ration (OR) is identified to measure therndegree of association between the occurrence of mental illness and demographic-socioeconomicrndeterminants controlling level of urbanization.rnThe respondents were diagnosed for seven categories of mental illnesses; depression was thernmodal (35%) mental disorder followed by general anxiety disorder (14%) and any psychologicalrndisorder (10%). Of all the total patients (n=300) 68% were female and the mean age was 29-39rnyrs. 67% of the respondents were below high school level and non-married and about 62% ofrnthem responded as they have lived for less than 5 yrs in the city. Regarding socioeconomicrndeterminants, about 77% of the respondents live in houses that are neither theirs nor rented fromrnthe government and and about 67% of them earn monthly income less than or equal to 600 birr.rnThe occurrence of mental illness is found to be associated with most demography andrnDemographic and Socioeconomic Determinants of Mental Health Disorder in Adult Residents of Addis Ababarnsocioeconomic determinants at 0.05 significant levels regardless of the level of urbanizationrnexcept religion and family size.rnAccording to the findings partly discussed above, we can conclude that the prevalence of mentalrnillnesses is determined by age, education level, years in the city, individual's role in the family andrnmarital status. MHO is more prevalent among young adults than old adults, among those who arernbelow high schools and the non-married one and lower socioeconomic status is found to increasernthe vulnerability to different mental health disorders. The occurrence of mental illness in the adultrnresidents is determined by their demographic and socioeconomic characteristics than the level ofrnurbanization of the city.rnKey wordsrnMental Health, Urban Livelihood, Adult Residents, Cross-Sectional Survey, SocioeconomicrnDeterminants.