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Vegetation has a significant effect on the purifying processes in storm-water ponds. As pond hydrodynamics are also strongly affected by vegetation, it is necessary to understand flow and mixing processes in vegetated ponds for effective treatment design. In this paper the Residence Time Distribution (RTD) and related indices are discussed, and selected recent field and laboratory studies on vegetated ponds are reviewed. Selected RANS CFD (Reynolds-averaged Navier–Stokes Computational Fluid Dynamics) studies, which investigate pond geometry, are outlined. Those studies which investigate the effects of vegetation are divided into two types, first those which consider it as bed roughness or a retarding force, and second, those which consider it as a flow zone. The conclusions from the first approach are that it is sufficient to predict average hydraulic features for flood studies but insufficient for investigating mixing effects of vegetation. Recent publications have suggested that the second approach, i.e. considering vegetation as a porous media, may be more suitable. However, the most recent study highlighted certain limitations, as well as providing some preliminary suggestions for overcoming them. This discussion reinforces the need for further comprehensive research into this, and alternative, approaches.