The spontaneous fermentation of butter produces a highly fragrant product called smen. The short chain fatty acids (C4 to C10) have been traditionally considered the main aromas of this product but our work on the volatile fraction characterisation using SPME GC/MS showed that other products may also be important. Indeed, 183 different volatile compounds were detected belonging mainly to carboxylic acids, esters, ketones, nitrogen compounds and terpenes. However, only 19 compounds were common to more than 50% of the samples. These include short chain fatty acids (C4 to C10), their esters and short chain methylketones (C5 to C11). Despite their high levels in all samples, the amounts of C4 to C10 free fatty acids could not explain the differences in preparation and consumer appreciation of the samples. In contrast, the levels and nature of some methylketones and esters, particularly butanoic and hexanoic ethyl esters and 2-pentanone, seem to better reflect the effects of salt, thyme, acidity and consumer preferences.