Eight constructed wetland ponds treating pulp mill effluent were monitored for removal of biochemical oxygen demand (BOD) and total suspended solids (TSS). Matched pairs of ponds differed by retention times and vegetation types. Analysis showed that variations over time between pairs of similar ponds were small. Performance of similarly designed constructed wetlands should be similar. TSS effluent concentrations varied by vegetation type, while BOD effluent concentrations varied with season.