In this presentation we will discuss why gender differences matter in addiction diagnosis and treatment. 1. We will review the definition of gender and sex and why this is important to recognize in addiction treatment. 2. We will review how culture plays a role in substance use and outline how special populations are affected by substance use. 3. The biology of sex differences in addiction and treatment will be reviewed to include hormones and neurobiology. 4. We will review the risk factors for addiction and how to develop a substance use treatment plan addressing gender and sex differences.