Two-phase flow in a shallow bubble column (radius equal to the height) was studied. The primary objectives were to study both the effect of the: free surface on the whole flow mode and the three-dimensionality in the whole domain. Air bubbles were injected through a central porous bottom wall of a cylindrical water tank. The flow pattern was visualized with dispersed aluminium particles. The velocity of the liquid phase was measured with a laser-Doppler velocimeter. The system was numerically analysed with a dispersed flow model. The inertial terms in the momentum equations were approximated by the QUICK scheme. Two models for the top surface were employed, namely either slip or non-slip conditions. The computed result with non-slip conditions agreed fairly well with the experimental result. A three-dimensional calculation was carried out with non-slip conditions for the top water surface. The calculated flow pattern agreed better with the experimental pattern than the two-dimensional calculation. In the results, two spiral vortices moving vertically were found outside the central upward flow. The flow was strongly three-dimensional, even though the vessel was shallow.