In this paper we explore the use of two different global multiregional input-output databases (GTAP-MRIO and WIOD) for the calculation of the global carbon emissions embodied in the final demand of nations (carbon footprint). We start our analysis with a description of the main characteristics of the databases and comparing their main components. Then, we calculate the carbon footprint with both databases and identify (from a global perspective) the most relevant factors underlying the resulting differences using structural decomposition analysis. The main conclusion that can be drawn is that, on average, certain elements of both databases can be said to be similar in around 75% to 80%, being only a few elements in each table the main drivers of the major differences. The divergences in the datasets of four countries explain almost 50% of the differences in the carbon footprint (USA 19.7%, China 18.1%, Russia 6.4% and India 4.3%). Industry wise, 50% of the differences can be explained by the divergences in three industries: (electricity 32.7%, refining 9.9% and inland transport 7.1%).