We have investigated the thermal and the chemical stabilities of In-and N-polar InN surfaces by treating InN films in several environments: annealing in vacuum, etching in KOH solution, and irradiating with atomic hydrogen (H*). For the annealing case, In-polar films mostly disappeared after 5 min at 550 °C and In-droplets of various sizes were left on the surface of the samples, whereas N-polar films showed no noticeable change in thickness and only tiny In-droplets were formed on the surface. For the KOH case, N-polar films developed rough surface morphologies by the emergence of hexagonal pyramids, whereas In-polar films were not etched noticeably. In-polar films also exhibited a much lower reactivity to H* than that of N-polar films. As a result, the N-polar surface was thermally more stable than the In-polar surface, whereas the In-polar surface appeared to be chemically more stable than the N-polar surface.