The third part of the guidelines of the Polish Psychiatric Association presents principles for the management of patients with schizophrenia and co-occurring substance use disorder (dual diagnosis). The authors emphasize that effective treatment requires an integrated care model led by a single multidisciplinary team, ensuring continuity of care, assessment of adherence to treatment recommendations, and consideration of psychosocial factors. A key element is relapse prevention through monitoring early warning signs, implementing individualized action plans, appropriate pharmacotherapy (including long-acting antipsychotics for patients with poor adherence), concurrent treatment of substance use disorder, and active family support. The guidelines also discuss management in specific situations, such as pregnancy, adolescence, advanced age, and comorbid somatic diseases, highlighting the need for individualized therapy and close collaboration among specialists. Treatment effectiveness should be assessed in a multidimensional manner ‒ through control of schizophrenia symptoms, reduction in substance use, and improvement in quality of life and social functioning. The document concludes with a set of practical recommendations covering diagnosis, pharmacotherapy, psychotherapy, safety monitoring, and strategies for harm reduction and relapse prevention.