Recurrent laryngeal nerve (RLN) injury is a well-known and serious complication to thyroid surgery. The objective was to estimate the frequency of post-thyroidectomy RLN palsy and to identify possible risk factors. Based on the Danish national thyroid surgery database, 6,859 patients treated with thyroid surgery from 1 January 2001 to the 31 December 2008 at the Danish departments of ENT-HNS were analyzed. Unilateral RLN palsy was found in 2.1 % and bilateral in 0.1 %. In benign histology, RLN palsies were registered in 1.3 %. Malignant histology and accordingly neck dissection were the most predominant risk factors with a relative risk (RR) of 5.4 and 5.8, respectively. In benign cases previous performed thyroid surgery had a RR of 10.4. High volume departments with more than 150 thyroid procedures per year seem to perform significantly better. Malignant histology, neck dissection and previous performed thyroid surgery are the strongest predictors for RLN palsy and patient information should be given accordingly. Incomplete resections should be reserved for isthmectomy only. Centralization of thyroid surgery in larger units might improve quality.