The incidence of non-tuberculous mycobacteria (NTM) disease is thought to correlate negatively with the tuberculosis (TB) burden. To determine the recent trend in the number of patients with NTM lung disease at a tertiary referral hospital in South Korea, where the incidence of TB has been stationary, a retrospective analysis was performed. From 2002 to 2008, the number of patients with NTM lung diseases increased from 82 to 133, while the number of TB patients decreased from 436 to 276. NTM lung diseases might be increasing in South Korea despite the stationary incidence of TB.