Molecular distillation (MD) was applied for enrichment of cuminaldehyde and p-mentha-1,4-dien-7-al in cumin oil in the present study. A central composite rotate design was used to optimize the experimental parameters: distilling temperature and distilling pressure. The effects of distilling temperature and distilling pressure on distillates yield, contents of cuminaldehyde and p-mentha-1,4-dien-7-al were systematically studied by response surface methodology and perturbation plot. Results indicated that distilling temperature and distilling pressure were two important factors in MD process, both of them and their interaction term had significant effects on all the responses (P < 0.05). and the effect of distilling pressure was more significant than distilling temperature. The optimum conditions maximizing yield, and purities of cuminaldehyde and p-mentha-1,4-dien-7-al were found as distilling temperature of 30 degrees C and distilling pressure of 19 Pa, the distillates yield was 81.23% and contents of cuminaldehylde and p-mentha-1,4-dien-7-al were 38.93% and 55.75%, respectively. (c) 2012 Elsevier B.V. All rights reserved.