In this chapter, the main content is to summarize the similarities and differences between substance and non-substance addictions in several aspects, involving definition, mechanisms, diagnosis, and treatment. We try to display the complete picture of addictions in a brief but comprehensive way. Mechanism includes molecule and neural circuits, genetics, neuroimaging, and cognitive psychology; diagnosis includes diagnostic criteria, diagnostic scales, biochemical diagnosis, and new diagnostic techniques; treatment includes drug therapy, physical therapy, traditional Chinese medical therapy, nutrition support therapy, psychotherapy, and cognitive behavioral therapy. This chapter also covers some prospects that will induct future studies on addiction. We aim to provide the researchers and graduate students with a better understanding of substance and non-substance addictions.