Background: Patients' understanding of their illness is of great importance for recovery. Lacking understanding of the illness is linked with the patients' level of reflection about and interest in understanding their illness. Objective: To describe patients’ variations of reflection about and understanding of their illness and how this understanding affects their trust in themselves or others. Method: The study is based on the “Illness perception” model. Latent content analysis was used for the data analysis. Individual, semi-structured, open-ended and face-to-face interviews were conducted with patients (n=11) suffering from a long-term illness diagnosed at least six months prior to the interview. Data collection took place in the three primary healthcare centres treating the participants. Results: The results show variations in the degree of reflection about illness. Patients search for deeper understanding of the illness for causal explanations, compare different perspectives for preventing complication of their illness, trust healthcare providers, and develop own strategies to manage life. Conclusion: Whereas some patients search for deeper understanding of their illness, other patients are less reflective and feel they can manage the illness without further understanding. Patients' understanding of their illness is related to their degree of trust in themselves or others. Patients whose illness poses an existential threat are more likely to reflect more about their illness and what treatment methods are available.