The present study was aimed to examine whether functional capacity among the urban home-dwelling older adults associates with health-related behavior. We also examined whether health-related behavior and certain diseases can be seen as mechanisms explaining socioeconomic disparities in functional capacity. A cross-sectional survey from 2008 was used to study 1395 older adults aged 75 and over living in one of the central areas of the city center of Helsinki, the capital of Finland. Associations of activities of daily living (ADL) with, smoking, food habits, physical activity, socioeconomic status and certain diseases were tested using ordinal regression model. Current smokers had slightly poorer functional ability than non-smokers among men. Those who did not use vegetables and/or fruits daily had a poorer functional capacity than daily users. Physically inactive respondents had clearly poorer functional capacity in comparison to active ones. Those with lower education had poorer functional status than higher educated irrespective of health-related behaviors and certain diseases. As health-related behaviors are modifiable, intervention programs should be targeted at all older adults with or without health problems.