Vegetation in cities provides several services including habitats for wildlife and reducing heat in highly urban areas. Urban vegetation can also remove carbon dioxide (CO2) from the atmosphere, potentially offsetting some of the greenhouse gas emissions from cities. Therefore, it is important to accurately determine exchanges (fluxes) of biogenic CO2 in and around urban areas. In this work we adapt and apply urban vegetation models to estimate vegetation CO2 fluxes in and around Canadian cities. Specifically, we modified two existing urban vegetation models; the Urban Vegetation Photosynthesis and Respiration Model (UrbanVPRM) and the Solar-induced chlorophyll fluorescence for Modelling Urban biogenic Fluxes (SMUrF) model. The updates we made significantly improved the agreement between the models and with biogenic CO2 flux measurements in Southern Ontario, and increased the spatial resolution of the SMUrF model. We applied the updated SMUrF model to the Greenbelt of Ontario, a region designed to protect Ontario's natural and crop lands from urban expansion. We found that vegetation in the Greenbelt is an important sink of CO2, but this varies significantly depending on the location and land-use type. We further discuss the impacts of converting these lands to urban areas on the biogenic CO2 fluxes. Finally, we apply the updated SMUrF model to the most populated cities in most Canadian provinces. We identified trends and found that temperature, precipitation, and the amount of paved surfaces are all important factors in explaining differences in biogenic CO2 fluxes between the studied cities.