Metals are usually covered by a thin metal oxide. Surface acid-base reactivity of this surface layer is still an open problem. In this work, this problem has been approached by wettability measurements and by chemical reactivity on titanium sheets. Wettability is an average surface property measured on a macroscopic scale. Chemical reactivity, which depends on surface sites, has been explored by adsorption of basic and acid molecules, acting as probes, and has been subsequently analysed by XPS. Both analysis suggest that titanium sheets show basic reactivity. A comparison is made with the reactivity of a thermally oxidised specimen where the thick oxide layer produced showed a weak acid reactivity. Surface reactivity of titanium sheets is suggested to depend on the oxide thickness.