The phenomenon of creating a breeding association by the barred warbler (Sylvia nisoria) and the red-backed shrike (Lanius collurio) was documented relatively long ago by several researchers. Some of the authors suggest that this phenomenon is a result of similar habitat requirements rather than a product of active selection. The main goal of this study was a quantitative analysis of differences and similarities in selection of breeding habitats by both species in the area of their sympatric occurrence. Research was carried out in the years 2009–2011 in the study plot located in the Middle Vistula Valley (central Poland). The red-backed shrike preferred shrubs and open areas, however, it avoided woods and waters. The only habitat strongly preferred by the barred warbler was bushes, and this species avoided waters, woods and open areas. Neither species nested in places with a thick tree concentration. Because of differences in their feeding strategy, as opposed to barred warblers, red-backed shrikes preferred habitats with low vegetation and a low concentration of shrubs. In nest location selection, the red-backed shrike clearly preferred hawthorns, whereas the barred warbler nested also in other species of bushes. As compared with warblers, shrikes more often preferred to nest in high bushes. The knowledge of the red-backed shrike's and the barred warbler's optimal habitat requirements can provide useful guidelines for future conservation projects involving these vulnerable birds.