Both Lewis and Bronsted basic properties of magnesium oxide (MgO) are, respectively, studied by adsorption of CO2 and methanol CH3OH. Various chemical synthesis of pure magnesium oxide (commercial, sol-gel and precipitation methods) are used. The influence of small amounts of alkaline (Na+ and Li+) and alkaline-earth (Ca2+) cations is also reported. The amount and the strength of Lewis and Bronsted basic sites are determined by heat flow microcalorimetry. As observed with doped MgO samples, the amount of basic sites is increased but the strength of these sites remains the same. The observed strength of Bronsted sites is generally lower than the Lewis ones. These measurements reveal trends based on the synthesis process that can have an important impact on these basic properties. (C) 2011 Elsevier B.V. All rights reserved.