Objectives: To report a follow-up of patients following the surgical anti-infective treatment of peri-implantitis and to identify possible risk indicators for the progression of disease during supportive peri-implant therapy. Material and Methods: Following peri-implant surgery, 41 patients (213 implants) were enrolled in a supportive peri-implant therapy. At the 2-year follow-up, two groups of patients were identified, with or without residual peri-implant pockets (responding and non-responding group). Eighteen patients (85 implants) of the non-responding group were followed for further 8 years. Results: At the 2-year examination, 73 of the 117 treated implants (62.4%) presented healthy peri-implant condition, while 44 (37.6%) presented persisting peri-implantitis associated with substantial bone loss before treatment. The 10-year examination of the non-responding group revealed that 1) 84% of the implants that regained health following surgery remained healthy during the entire observation period; 2) 66% of the implants with residual pockets following surgery maintained stable peri-implant condition; and 3) 29% of all treated implants showed disease progression, and 11 of those were extracted. Presence of pockets at 3–4 sites of the implants was identified as risk indicator for progression of peri-implantitis. Conclusion: The peri-implant health achieved following therapy was maintained for most of the implants during the follow-up. Residual pockets were a frequent finding at implants with substantial bone loss before treatment. Presence of pockets around the entire circumference of the implants resulted as a risk indicator for further disease progression. The probability of progression of peri-implant disease increased with increased observation time. © 2021 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd