•This study calculates carbon footprints of four Chinese megacities.•CO2 emissions related to urban consumption are largely outsourced to other regions.•Addressing urban consumption plays a key role in climate change mitigation. China has experienced rapid urbanization in the last three decades, with more than half of the population living in cities since 2012. The extent of urban production and urban lifestyles has become one of the main drivers for China's CO2 emissions. To analyze drivers of CO2 emissions we use a consumption-based accounting approach that allocates all emissions along the production chain to the product and place of final consumption, whereas a production-based approach would allocate all emissions to the place of origin. In this study, we focus on the spatial distribution of production activities leading to CO2 emissions across China as a consequence of final consumption in four Chinese mega cities: Beijing, Shanghai, Tianjin, and Chongqing. Urban consumption not only causes a large amount of emissions within its territory, but also imposes even much more emissions to its surrounding provinces via interregional supply chains. Results show that more than 48% of CO2 emissions related to goods consumed in Chongqing and more than 70% for Beijing, Shanghai and Tianjin occurred outside of the respective city boundary. In addition to the usual focus on efficiency, our analysis adds insights into the causes of CO2 emissions by looking at the drivers and types of consumption. Addressing consumption patterns in China's cities is critical for China's low carbon development.