Habitat subdivision may facilitate the persistence at low densities of both predator and prey populations. But habitat subdivision may also allow herbivores to escape from predators and therefore reach higher local densities. The outcome will depend on the dispersal behaviour of organisms. The effect of habitat subdivision on populations of aphidophagous coccinellids Eriopis connexa and Hippodamia variegata and their prey Brevicoryne brassicae was evaluated in crops of Brassica oleraceae. In particular, the following responses were analysed: a) density/plant of herbivorous and predatory insects, b) colonisation of herbivorous and predatory insects, c) movement between plant patches and residence time of predators, d) in situ recruitment of predators, and e) final weight of plants. Nine continuous and subdivided plots of B. oleracea were set up following a 3 x 3 completely randomised block design. The three treatments were: a) continuous, b) subdivided plus weeds, and c) subdivided plus cloth barriers. Density per plant of herbivorous and predatory insects was lower in subdivided plus barriers habitats. Colonisation by herbivores and predators was more rapid in continuous or subdivided plus weeds habitats. Residence time and in situ recruitment of predators was greater in continuous habitats. Plant weight was greater in subdivided than continuous habitats. Therefore, habitat subdivision, particularly when patches were more isolated, negatively affected the population densities of both herbivorous and predatory insects. This is likely due to lesser colonisation and in situ recruitment, and greater emigration of insects in those subdivided habitats.