This article briefly reviews the literature on the relationship between social network and mental health, and presents a theoretical framework outlining the role social networks may play in explaining the differential mental health service utilization rates between Maori and European people of New Zealand. By buffering individuals from the ill effects of stressful events, social networks may have a protective effect on people's mental health. In addition, social networks influence the way people with mental illnesses use mental health services. An inverse relationship between the size of an individual's social network and the rate of utilization of in-patient services has been reported. Despite having a larger and presumably more supportive social networks, Maori are over-represented in mental health service utilization statistics. Using the Maori example, we demonstrate that ethnic differences exist in the structure of social networks and the provision of social support to their members. Such differences may be based on the degree of emphasis placed on kinship or on individualism by cultures and on the receptivity or prejudice of the host community. We examine the sources of stress on Maori social networks that may adversely affect the network's ability to support its members experiencing mental illnesses. Caution must be exercised in using service utilization rates as measures of the mental health needs of different ethnic groups because of problems with help seeking and the detection of mental health issues in different ethnic groups.