There is growing awareness that mental illness is surrounded by negative attitudes and stigmas. The aim of the present study was to investigate factors associated with mental health nursing staff's attitudes towards persons with mental illness. Data were collected from 256 mental health nursing staff employed by one county council and 10 municipalities. The findings show that staff have more positive attitudes towards persons with mental illness if their knowledge about mental illness is less stigmatized, their work places are in the county council, and they currently have or have once had a close friend with mental health problems. The multiple regression model explained 16% of the variance; stigma-related knowledge and employer had significant Beta-coefficients. To account for unknown correlations in data, a linear generalized estimating equation was performed. In this model, stigma-related knowledge and employer remained significant, but a new significant factor also emerged: personal contact, i.e. currently having or having once had a close friend with mental health problems. This indicates correlations at unit level in the county council and in the municipalities. The conclusion is that more favourable attitudes among staff towards persons with mental illness could be developed and transmitted in the subculture at work places.