The Organocell process is the most advanced organosolv pulping process on a semi-technical scale. Delignification is performed by two-stage cooking involving methanol/water in the first stage with additional NaOH in the second stage. In this study spruce and pine lignins from the Organocell pilot plant and from laboratory cookings in a 20 1 batch digester were characterized by means of elemental analysis, determination of nonlignin portions such as proteins, sugars and ash, and of functional groups (OH, CO, COOH, OCH3). While first stage samples contained a considerable amount of impurities identified as organic nonlignin substances, second stage lignins showed characteristic changes in elemental composition and functional groups, except for the methoxyl groups, as reaction time progressed.