This paper explores the relationship between CO2 emissions and economic activity for 31 countries (28 OECD, Brazil, China, and India) during the period 1950 to 2006 using cointegration analysis. Single country long run relationships are estimated, and equality in the functional form, the parameters, and the turning point, when appropriate, are rejected. This confirms the relevance of considering the differences among countries in the relationship between air pollution and economic activity to avoid wrong estimations and conclusions. (C) 2012 Elsevier Ltd. All rights reserved.