The term periodontitis encompasses a wide spectrum of inflammatory conditions of the gingiva, bone and periodontal ligament, i.e. all structures surrounding the teeth. Patients with periodontitis regularly receive implants, although the peri-implant tissues are susceptible to the same risk factors that cause periodontitis. Numerous short-term research have shown similar rates of implant survival in patients with or without a history of periodontitis, while more recent, longer-term research have noted a significantly increased incidence of peri-implant complications in patients with periodontitis. The results indicated a cause-and-effect relationship between plaque on implants and peri-implant mucositis. The sensitivity of soft and hard tissues to the accumulation of plaque around implants is similar to that around teeth. Understanding the impact of periodontitis on peri-implant health is essential for the implementation of successful implant-prosthetic therapy. Poor oral hygiene, periodontitis in the anamnesis and smoking proved to be the most important risk indicators for the development of peri-implantitis. Other factors influencing plaque build-up, such as excess cementum and design of the prosthetic restoration, are also strongly associated with the development of peri-implantitis. When planning implant prosthetic therapy in patients with periodontitis, it is crucial to recognize and take into account all risk factors that could compromise the success of the therapy itself, be they past, present or future.