Functional assessment is important to determine whether restored and created wetlands are similar to natural ones. We investigated ecosystem processes (decomposition, biomass production) and some aspects of biogeochemical cycles (plant uptake of nitrogen and phosphorus, litter N immobilization) in a population of natural and created (mitigation) wetlands. Our goals were to quantify ecosystem processes and compare some biological and physical characteristics, in order to assess the relative performance of created wetlands. The biological and biogeochemical characteristics of the natural and created sites were substantially different. Decomposition rates for both in-situ and control litter and tissue nutrient concentrations were higher in the natural wetlands, with final decomposition rate constant values (k (d⁻¹)) averaging 0.009 for natural and 0.006 for restored sites over approximately a one-year incubation period. Aboveground biomass production was also significantly higher in the natural sites, averaging 347 g m⁻² compared to 209 g m⁻². Concentrations of soil percent organic carbon, percent nitrogen, and plant available P (µgP g soil⁻¹) were significantly higher in the natural sites. Lower soil nutrient content in the created wetlands appears to propagate through the system resulting in low tissue nutrient levels, less biomass accumulation, and slower rates of decomposition.