We investigated the 6-day effect of short-term (2 h at the end of the night – DROP) and continuous all-day (CLT) temperature reduction to 12 °С on lipid and fatty acid content, and cold resistance in cucumber (Cucumis sativus L.) plants at early stages of the ontogeny. Comparison of plants from the experiments to the control revealed differences in the response of cotyledons exposed to DROP and CLT at the level of the membrane lipid component. Continuous exposure to a temperature of 12 °С promoted cold resistance of cotyledons and raised total lipid and fatty acid content without changing the proportions of unsaturated and saturated fatty acids any significantly. At short-term exposure to 12 °С, the considerably higher cold resistance was accompanied by a decrease in total lipids and fatty acids, while their unsaturation increased owing to a rise in linolenic acid content. It is hypothesized that significant enhancement of cold resistance in cucumber cotyledons under DROP is related to daily periodic induction of one of ω-3-desaturases, which facilitates increased synthesis of linolenic acid.