Introduction. The Neodymium:YAG laser in sinus surgery has been regarded as potentially hazardous to orbital and skull base structures. However, these are parameters under which a Neodymium:YAG laser can be used safely for the treatment of pathologic changes in the paranasal sinuses. Patients and methods: Following endonasal-microscopic sinus surgery for chronic sinusitis in 507 patients, we saw recurrent polyps, scar formation or persistent granulation tissue in 57 patients (11,2%) within 30 months. These patients were treated by minimally invasive endoscopic Nd:YAG-laser ablation. We applied a self-regulated power delivery system with a maximum power output of 10 W in contact mode via a 0,6 mm glass fibre. Results. Nd:YAG laser sinus surgery can be done as an out-patient procedure under local anaesthesia. Four patients asked for general anaesthesia. Local haemorrhage interfered in three patients. Laser-specific complications (thermal damage, skull base or orbital perforations) were recorded in none. Histology showed no deep necrosis in any of the laser sites. Conclusion: Using a self-regulated power delivery system at low power rates in contact mode, the Nd:YAG-laser is a safe tool even in such delicate regions as the paranasal sinuses. Patients profit from early ablation of local recurrences, before extensive revision surgery becomes inevitable.