The study asks how well are cities doing in reducing their greenhouse gas emissions. Data from six cities with repeat GHG emission inventories for the period 2004-2009 is examined: Berlin, Boston, Greater Toronto, London, New York City and Seattle. All of the cities are reducing their per capita GHG emissions, primarily through changes to stationary combustion. On average the cities are reducing per capita emissions by 0.27 t CO(2)e/capita per year; this is about the same average rate as the cities nation states, although the cities are reducing emissions faster in percentage terms. (C) 2012 Elsevier Ltd. All rights reserved.