Via the discrete element method, a three-dimensional partially filled rotating drum operating in the rolling regime is numerically simulated to investigate the solid residence and inter-region exchange behaviors in the active and passive regions, and their dependence on the operating parameters of rotating speed and particle diameter ratio of the binary-size mixture. The results demonstrate the effects of size-segregation of the binary-size mixture: (i) for both particle displacement and residence time, the magnitude of large particles are greater, and the magnitudes in the passive region are greater than that in the active region; (ii) the solid exchange rate between the two regions is greater for the small particles; (iii) although the solid exchange rate of each particle type evolves with time due to the evolving size segregation, the exchanging rate between the active and passive regions is proven to be global parameter, which is not influenced by size-segregation; (iv) changes in the rotating speed has a greater influence than that in particle diameter ratio in the ranges investigated. Collectively, these results shed more light on the impact of size segregation of a binary-size mixture on the characteristics of the rotating drum. (C) 2017 Elsevier Ltd. All rights reserved.