The shapes and dynamics of single bubbles rising through viscous fluids are studied using the SPH (Smoothed Particle Hydrodynamics) approach. This fully Lagrangian, particle-based method is applied to compute the complete two-phase flow, both inside the bubbles as well as around them. For that purpose, a multi-phase formulation of the SPH method that can address large density differences is retained, while surface tension effects are explicitly accounted for through a CSF (Continuum Surface Force) model. Numerical simulations have been performed for different regimes (corresponding to different relative importance of surface tension, viscosity and buoyancy effects) and the predicted topological changes as well as the terminal velocity and drag coefficients of bubbles are validated. The numerical outcomes are assessed not only with respect to reference experimental data but also with respect to other numerical methods, namely the Front-Tracking and the Lattice Boltzmann Methods. It is believed that this study corresponds to a new application of SPH approaches for two-phase flow simulations and results reveal the interest of this method to capture fine details of gas-liquid systems with deformable and rapidly changing interfaces. (c) 2012 Elsevier Ltd. All rights reserved.