Achnanthidium druartii differs from similar species A. deflexum and A. alpestre by the lanceolate shape of the valve and the large difference in stria density in the valve center, as compared to the valve ends. Achnanthidium pyrenaicum and A. eutrophilum can be easily distinguished from A. druartii by their smaller size range. Achnanthidium rivulare is distinguished by its linear-elliptical valve outline.