The occurrence of radial cracks in Sakhalin spruce (Picea glehnii), differences in the degree of cracking among five habitats, and the relationship between cracks and wood density were investigated in a total of 79 logs collected from five sites in Hokkaido, Japan. The cracks were divided into two types: intra-ring radial cracks that were restricted to cracks within an annual ring and larger radial cracks that extended beyond a single annual ring. The number and the longitudinal length of cracks in log varied depending on habitat, and it was considered that the cold temperature conditions in winter might affect the incidence and length of cracks. The results of soft X-ray densitometry showed that the annual ring density with cracks was lower than the annual ring density without cracks. It is considered that this low wood density affected the occurrence of cracks.