Constructed treatment wetlands are a practical, low-cost method for treating agricultural wastewater. During the treatment process, vegetated wetlands can act as both a source and sink of greenhouse gases. Thus, there are trade-offs between wastewater treatment and air quality. The objective of this research was to shed light on the overall source/sink status of vegetated surface flow and subsurface flow wetlands over the course of a full year. To do so, six pilot-scale treatment wetlands were constructed (6.6 m², three of each wetland type). The wetlands were loaded with high-strength dairy wastewater. Each wetland was contained within a greenhouse-like steady-state chamber, which enabled gas fluxes to be calculated using a mass-balance approach. Methane (CH₄) and nitrous oxide (N₂O) concentrations were continuously measured using tunable diode laser trace gas analyzers. Carbon dioxide (CO₂) was continuously measured using an infrared gas analyzer. Preliminary results indicate that there can be large differences in emissions from surface and subsurface flow systems. Gas fluxes show strong seasonal patterns.