wood samples with Klason lignin ranging from 16.5% to 24.5%, and acid soluble lignin 3.8%–5.7% (extractive free wood) were tested. The lignin absorptivities were measured using a MWL and samples with known Klason and total lignin content: values of 18.47 lg−1 cm−1, 20.77 lg−1 cm−1, 25.57 lg−1 cm−1 were obtained. When the lignin content is calculated based on the MWL absorptivity, results are approximately 3 abs.% higher than the lignin content determined by the standard acid method. The results of total lignin determination (Klason plus acid soluble) can be reproduced with high precision by the acetylbromide method.