Community assembly can be viewed as the trajectory, regarding species composition and community structure, a community exhibits over time as new species fail or succeed in establishing. Community assembly in saproxylic (wood-living) Coleoptera was studied in two boreal coniferous forest types, recently burnt forest and old-growth forest, by exposing 88 Norway spruce, Picea abies, bolts (0.5 m long pieces of bole) to colonization for increasingly longer times (0.5, 1, 2, 4, and 8 weeks). The final 8-week communities diverged in species composition but converged regarding community structure measures, such as species richness. In both forest types cambivores dominated the final state. Assemblages became increasingly similar in species composition along the assembly trajectory in old-growth forest but not in burnt forest. Assemblages in the two forest types followed different trajectories regarding species composition. They also showed clear differences in evenness and species identity of the bolt-dominant species (species with the highest abundance in a particular bolt). Overall, burnt-forest bolts had a more open community with higher evenness and a more diverse selection of bolt-dominants, while old-growth bolts had a more closed community highly dominated by Dryocoetes autographus (Scolytinae), a species common also in managed forest. During assembly, burnt-forest bolts had a higher proportion fungivores than old-growth bolts. Proportion predators was higher during assembly than in the final state in both forest types. The last two results showed that guilds important during assembly were found in lower proportions in the final assemblages.