Haematophagous dipterans belonging to 10 genera – Aedes (12), Anopheles (14), Armigeres (01), Culex (09), Toxorhynchites (01), Uranotaenia (01), Sergentomyia (02), Phlebotomus (01), Atylotus (01) and Tabanus (03) were encountered from 12 localities under 6 blocks of Dehradun district (Uttarakhand) during January 2011 to December 2012. The Culicines (50.69%) were more dominant than the Anophelines (38.9%), Toxorhynchites (1.72%), horse flies (6.63%) and sandflies (2.01%). The following species viz., Toxorhynchites splendens and Phlebotomus argentipes have been recorded for the first time while Aedes pseudotaeniatus as reappeared species from the study area. Species diversity is represented through Species richness (S), Shannon index (H) and Shannon Eveness (E) among Aedes, Anopheles, Culex, Sandfly and Horsefly. The species richness (S) and evenness (E) were found as 12, 0.65; 14, 0.84; 09, 0.74; 3, 0.61 and 4, 0.78 respectively by Aedes, Anopheles, Culex, Sandfly and Horsefly. Highest Shannon index was shared by Anopheles (2.214) followed by Culex (1.639), Aedes (1.631), Horsefly (1.085) and Sandfly (0.672) in succeeding order.