Purpose: To compare the incidence of complications related to onlay bone grafts (OBGs) and sinus lift operations (SLOs) among smokers and nonsmokers. Materials and Methods: Data from 143 operations performed during the years 1995 to 2003 were analyzed. There were 64 OBGs and 79 SLOs. Patients were divided into 3 groups: nonsmokers, mild smokers (up to 10 cigarettes per day), and heavy smokers (more than 10 cigarettes per day). Duration of smoking (less or more than 10 years) was recorded. OBG complications were classified as minor (hematoma, swelling, inflammation, or temporary paresthesia) or major (graft exposure or mobility). For the SLO, perforations of the schneiderian membrane were the main intraoperative complication; postoperative complications mostly consisted of swelling, acute or chronic sinus infection, or bleeding. Results: Of smokers having OBG, 50% experienced complications, compared to 23.1% of nonsmokers. Major complications were observed in one third of the smokers, compared to only 7.7% in nonsmokers. There was also a tendency toward complications in former smokers, although this relationship was not statistically significant. There was no relationship between SLO complications and smoking or a past smoking habit. Discussion: In the present study, smokers demonstrated significantly higher postoperative complications following OBG operations. Smoking did not influence the results in the SLO group. There was no statistically significant difference between complications and past smoking. This finding indicates that the risk of complications can be reduced up to the normal nonsmoker complication rate when smoking ceases. Conclusions: This study established a relationship between OBG complications and smoking in this patient population. A higher incidence of complications was found in the smoking group. There was no significant influence of smoking on SLO complications.