Statistics have shown that people who are HIV+ are more likely to smoke than HIV- people. This is unfortunate because HIV+ people already have a compromised immune system and smoking simply adds to the risk of greater ill health.
In healthy people smoking principally interferes with normal lung function. In people with HIV smoking additionally makes it more difficult to fight off serious infections. HIV+ people are living longer. Smoking, and smoking related conditions, will interfere with their long term quality of life.
HIV+ smokers are more likely to suffer complications from HIV medication, e.g. they are more likely to experience nausea and vomiting. Smoking also increases the risk of some long-term side effects of HIV disease and treatment such as osteoporosis; weak bones that can lead to fractures; and the risk of a heart attack or a stroke.