As an alternative to traditional prosthetic therapy, osseointegrated implants have been presented. The success of dental implant therapy depends largely on function and aesthetics, which may be spoiled by following peri-implant diseases. Periimplant mucositis is considered to be reversibile condition while peri-implantitis is seen as irreversibile condition. Peri-implantitis is defined as inflammation of supporting tissue (bone) in periimplant area and results in the loss of an implant. It is often compared to periodontitis but unlike periodontitis, it expands faster and is more difficult to treat. Poor oral hygiene, smoking, systemic diseases and early diagnosis of periodontal disease are risk factors for its development. It is manifested by clinical signs like bleeding after probing, pus formation and formation of pockets, swelling and inflammation of soft tisues, bone loss visible on X-ray, and ultimately implant mobility. The main topic of recent reserches is how to avoid implant loss. Depending on a defect around the implant, non surgical or surgical treatment is carried out. Mechanical cleaning of supra and subgingival plaque as well as antiseptic and antibiotic pocket rinse include non surgical treatment. Surgical treatment is indicated in extensive defects requiring mucoperiostal flap to remove inflammatory and granulation tissue, remodeling of the bone and filling defect with bone substitutes. Laser therapy and PRF are new methods of peri-implantitis treatment. We are still searching for a method of treatment that would enable complete healing of peri-implatitis.