The genus is notoriously difficult to differentiate from Cheilolejeunea for the uninitiated, sometimes even in the presence of fresh material. As a general rule, Lejeunea contains numerous oil bodies per cell whereas Cheilolejeunea has 1-2 (occassionally more) grape-cluster type oil bodies.

To differentiate Cheilolejeunea and Lejeunea from dried material, a close examination of the nature of the lobule teeth is necessary.