Implant therapy is an excellent solution for replacement of missing teeth. Like any medical procedure, it carries a risk of certain complications – most common are peri-implant infections. Risk factors for these diseases include poor oral hygiene, smoking, diabetes and previous periodontal diseases in the patient's anamnesis. Peri-implant mucositis is defined as a reversible inflammatory lesion of the peri-implant mucosa without loss of the supporting bone tissue, while peri-implantitis is manifested as inflammation coupled with bone loss. The goal of the treatment of this disease is to eliminate pathogenic microorganisms which inhabit the implant's surface and surrounding tissue causing inflammation. Two main methods of treatment are non-surgical and surgical therapy. The choice of treatment method depends on the level of bone loss around the implant. Mechanical debridement and the use of antiseptics are part of conventional, non-surgical therapy. Adjunctive treatment methods which help in eliminating bacteria include microabrasion of the implant surface, various disinfectants, use of antibiotics both local and systemic, lasers and photodynamic therapy, and finally ozone treatment. Surgical treatment methods are indicated in cases where major bone loss occured and it is necessary to elevate the mucoperiosteal flap in order to thoroughly remove inflammed tissue and bacterial deposits. They include resective and regenerative therapy. With the new classification and protocols for diagnostics and treatment of peri-implant diseases, treatment of these diseases will probably be more successful.