The spatial pattern in the occurrence of two congeneric beetle species in the fruiting bodies of the wood-decaying fungus Fomitopsis pinicola was studied in an old-growth boreal forest in eastern Finland. The aim was to characterize the spatial pattern of the common Cis glabratus (Coleoptera: Ciidae) and the rare C. quadridens. A 25-ha study area was divided into 25- × 25-m quadrats (n = 400), and all the dead and dying fruiting bodies of F. pinicola (n = 737) were taken to a laboratory to collect the two species living inside. The quadrat-based count data were analyzed using the Index of Dispersion (I_d), the SADIE Index of Aggregation (I_a), and Moran's I spatial correlograms. The frequency distribution of the quadrat counts of F. pinicola deviated from a random, Poisson distribution towards significant aggregation (I_d). There was also a significant spatial autocorrelation (Moran's I) at short (≤ 100 m) distances. The SADIE methodology, however, showed that there was no overall spatial structure in the arrangement of the counts of F. pinicola fruiting bodies, i.e., the observed quadrat counts were randomly distributed in the 25-ha study area. Similarly, the counts of the trees occupied by the two beetle species occurred randomly among the quadrats with fruiting bodies, and the pattern was consistent at all lag distances. These results indicate that both species can readily utilize available resources in the study area, despite their spatial location.