Different forms of crop resistance developed against major potato pests such as the Colorado potato beetle (CPB), Leptinotarsa decemlineata, may be variously compatible with biological control of secondary pests such as aphids. We compared the performance of the parasitoid Aphidius nigripes developing in the aphid host Macrosiphum euphorbiae, on five potato lines, including a transgenic `Superior-BT' line expressing the CryIIIA toxin of Bacillus thuringiensis, which is specific to Coleoptera; and the `NYL 235-4' line derived from Solanum berthaultii, characterized by relatively unspecific resistance to herbivores based on moderately-high density of glandular trichomes. The other lines tested were a `Kennebec-OCI' transgenic line expressing the protease inhibitor rice cystatin I (OCI), a potential resistance factor against coleopteran pests; and the commercial cultivars `Superior' and `Kennebec' used as controls. Parasitoid immature survival and adult size were reduced compared to controls when the wasps developed on aphids fed the `Superior-BT' potato. In contrast, parasitoid size and fecundity increased above control when the wasps developed on aphids fed the `Kennebec-OCI' potato. Parasitoids reached the adult stage faster and were more fecund on `NYL 235-4' than control lines. The results indicate that the different forms of potato resistance currently developed mainly against the CPB had various unexpected effects on aphid parasitoid fitness. These effects on the parasitoid were complex but were generally interpretable in terms of host aphid quality variation among potato lines used as food by the aphids during parasitoid development.