The aim of this study was to investigate the process of differentiation of terminal latewood tracheids near the cambium in silver firs (Abies alba) during dormant period. Samples of wood and cambium were taken from 10 apparently healthy mature trees in the middle of October, November and March. According to light microscopy, transmission electron microscopy and UV–microspectrophotometry, cambial cell-divisional activity was completed in all investigated trees in October, whereas process of differentiation was still ongoing in the youngest tracheids close to the cambium in trees with broader annual xylem growth rings. Layer S3 of the secondary cell wall and warty layer were not formed and inner parts of S2 layer of secondary cell wall were not yet lignified. Only four weeks later, in November, the cell wall formation and the lignification of terminal latewood tracheids close to the cambium were completed in all trees. No alterations were observed at the ultrastructural level between November and March samples. The cambial cell-divisional activity and also differentiation ended later in trees with broader annual xylem growth rings. However, differentiation of terminal latewood tracheids in all investigated trees was completed before winter.