Background: Shared values, norms and beliefs of relevance for safety in health care can be described in terms of patient safety culture. This concept overlaps with patient safety climate, but culture represents the deeprooted values, norms and beliefs, whereas climate refers to attitudes and more superficial manifestations of culture. There may be numerous subcultures within an organization, including different professional cultures. In recent years, increased attention has been paid to patient safety culture in Sweden, and the patient safety culture/climate in health care is regularly measured based on the assumption that patient safety culture/climate can influence various patient safety outcomes. Aim: The overall aim of the thesis is to contribute to an improved understanding of patient safety culture and subcultures in Swedish health care. To my beloved husband and my children, Magnus, Anton and Simon, I have no words for what you mean to me. We struggle every day together and share happiness and sorrows. Without your support and understanding I would not have been able to present this thesis. I love you and the most important thing in my life is that I am able to give you the feeling of being loved.