The composition of the uppermost surface layer of steel influences the coating properties. Surface segregation is generally considered to be one of the reasons for difficulties that can occur during hot dip galvanising. In the present work the surface composition of cold rolled, batch annealed steels and the change of composition after pickling, polishing, and shot blasting were studied using glow discharge optical emission spectrometry (GDOES) to explain the variations in the reactivity of the steels when undergoing hot dip galvanising. Surface segregation of all the elements included in the measurements (carbon, silicon, manganese, phosphorus, sulphur, chromium, nickel, aluminium, copper, and calcium) was observed. However, only silicon and phosphorus segregation clearly influenced the reactivity of the steel. Steel reactivity during galvanising could not be explained by the segregation of the outermost layer of the steel surface. Some elements (silicon, manganese, and aluminium) can have a relatively thick enrichment zone under the surface and, moreover, silicon concentration profiles can contain two peaks. These findings indicate internal oxidation of these elements, variation of which is a probable explanation for the different behaviour of the steels. Shot blasting, pickling, and polishing clearly influence the reactivity of the steels. Different pretreatments can remove the oxidised unreactive layer and/or increase the concentration of non-oxidised element (silicon). It is evident that the reactivity depends to some extent on the chemical composition of the steel under the topmost surface layer, a zone which is difficult to investigate by surface sensitive analysis methods (Auger spectroscopy, electron spectroscopy for chemical analysis). The present work showed that GDOES is a powerful tool for the analysis of relatively thick surface layers.