This thesis used attachment theory and the common sense model of illness as theoretical backgrounds to examine the mechanisms that contribute to the quality of the support seeking behaviour and social interactions between patients with type 2 diabetes and their partners. Specifically, this thesis examined actor and spouse effects of working models of attachment on health outcomes, and illness perceptions on health outcomes for both patients and partners. Furthermore, it determined if support seeking, supportive interactions, and negative interactions mediated between the attachment and health outcomes and illness perception and health outcomes. At study entry, 70 patients with type 2 diabetes and their partners completed measures on attachment, illness perceptions, support seeking, receipt of supportive interactions and of negative interactions, satisfaction with support received, and health outcomes. Health outcomes included psychological distress and physical health for patients and partners, and diabetes well-being for patients only. Six months later, participants again completed measures on supportive and negative interactions, satisfaction with support received, and health outcomes. The data were examined both cross-sectionally (including mediational analyses) and longitudinally. The cross-sectional analyses revealed a number of actor and spouse effects in the relationships between attachment and health outcomes, and illness perceptions and health outcomes. Patients who scored higher on attachment-anxiety experienced higher levels of psychological distress and lower levels of diabetes well-being. Also, the partners of these patients experienced higher levels of psychological well-being. Furthermore, covert support seeking behaviour and negative interactions were found to be significant mediators between patient attachment-anxiety and patient psychological distress and diabetes well-being. In addition, support satisfaction mediated the relationship between patient attachment-anxiety and patient psychological distress. Illness perceptions, specifically timeline cyclical perceptions, were also shown to be related to health outcomes, and receipt of negative interactions. Patients and partners who scored higher on timeline cyclical experienced higher levels of psychological distress. Also receipt of negative interactions mediated the relationship between timeline cyclical and psychological distress. Some significant changes over time found when the data were examined longitudinally. For example, patients who scored higher on attachment-anxiety at study entry experienced higher levels of psychological distress over time, and had a partner who also experienced higher levels of psychological distress over time. In addition, partners who scored higher on personal control and who had a spouse (patient) who scored higher on timeline cyclical at study entry experienced higher levels of psychological distress overt time. Taken together, both the cross-sectional and longitudinal findings emphasize the contribution of the partner and his or her interactions with the patient to patient well-being. In the same manner, the results also highlight the effect of the patient’s illness on the partner’s well-being. These findings have important practical implications, especially for practitioners who aim to design intervention to help patients and their partners better adapt to the patient’s illness.