In a great number of scientific articles on water quality improvement using constructed wetlands (CW) and riparian buffers zones (RBZ) at catchment scale, contradictory results are found. In most cases this is due to underestimating or even ignoring the role of the hydrological factor for water quality improvement. It has often resulted in biased estimates of buffering systems’ efficiency at catchment scale and, consequently, has caused planning and establishment failures, mistakes and inconsistencies in legislative acts and finally, it has influenced stakeholder's willingness to support these eco-technological measures. In this paper we present a short but critical overview of the potential of CWs and RBZs in water quality improvement at catchment scale and highlight the most important aspects to be considered when planning, establishing and managing these systems.