To fully appreciate the environmental impact of an office building, the transport-related CO2 emissions resulting from its location should be considered in addition to the emissions that result from the operation of the building itself. Travel-related CO2 emissions are a function of two criteria. The first relates to the location of the office relative to the location of the workforce, the market, complementary business activities (and the agglomeration benefits this offers), the availability and cost of transport modes. The second relates to the mode of transport between these locations and frequency of visits which, in turn, depends on the requirement for a physically present workforce and face-to-face contact with clients. This paper examines the commuting-related CO2 emissions that result from city centre and out-of-town office locations. Using 2001 Census Special Workplace Statistics which record peopleís residence and usual workplace and mode of transport between them, distance travelled and mode of travel were calculated for a sample of city centre and out-of-town office locations. The results reveal the extent of the difference between transport-related CO2 emitted by commuters to out-of-town and city centre locations. The implications that these findings have for monitoring the environmental performance of offices are discussed.