Experts in any field develop their expertise using both their training and experience. The nature of the expertise of the profession is a key essential of professionalism. The key to understanding professionalism is on two levels: first, what constitutes professionalism, and second, what gaps might highlight what a professional lacks, thus looking at expertise and professionalism both positively and negatively. In understanding the experiences, explanations and expressions of illness from the patient, the expert can engage with the patient, find common ground to explore, agree on goals of treatment and management plans and then keep these under review in regular discussions with the patient. This chapter shows that attitudes and professional attributes can be changed. Areas of expertise in psychiatry include culture; the ability to understand, co-ordinate and work co-operatively to provide comprehensive mental healthcare; the ability to understand ethical practice; and effective communication and education.