Whiteflies (Aleyrodidae) are major pests of crops in southwestern Nigeria, yet there is scanty information on diversity and distribution of these economic species. Therefore, a study of diversity and distribution of whitefly fauna was carried out in southwestern Nigeria in wet and dry seasons, between May 2007 and June 2012. Whiteflies were collected on crops and ornamental plants from 22 sampling sites, within the six states. Aleurodicus dispersus
Russel (Aleurodicinae) was the most distributed species of whiteflies on crops and ornamental plants. It was recorded in all the sampling sites and on 45 different families of plants in the region. Whiteflies were most diverse in the rainforest zone than any other zone in the region. The cosmopolitan Aleurocanthus woglumi
Ashby (Aleyrodinae) infested plants in the family Rutaceae more than any other species of whiteflies in the region. Citrus species was observed to host larger population of whiteflies than any other crop in the study area. Plant family, Euphorbiaceae, hosted the largest number of whiteflies (14 out of 35 whitefly species).