A serious pest of willow and poplar trees in Tehran region is clearwing moth, Paranthrene diaphana Dalla Torre & Strand (Lep.: Sesiidae) which cause to the drying of a branch or tree. In this study, of volatile compounds of willow were identified and reaction of P, diaphana to phthalic acid, phenylacetaldehyde and acid acetic were checked out. Willow volatile compounds both by chemical methods (adding dichloromethane or hexane to extract) and with absorbant poudery (Tenax trap) were isolated and identified by the GC/MS device. With the two mentioned methods, nine combinations of volatile were identified in the willow which 1, 2-Benzenedicarboxylic acid compound (Phthalic acid) in both methods was found, and so, the insect response to this substance was compared with phenylacetaldehyde and acid acetic. Reaction investigation of the insect to volatile compounds with two methods: wind tunnel or olfactometer, in conditions of lightness and scotophase, male and female, virgin and mating was performed separately. For analysis of data, in paired comparisons by a nonparametric method (Mann-whitne test) and in multi-level comparisons of the three trialed combinations the nonparametric method (Kruskal-wallis test) were used. The results showed that there was significant difference in the insect intracton among phthalic acid, phenylacetaldehyde and acid acetic (p<0.01), The insect is attracted to phthalic acid, Phenylacetaldehyde and acetic acid good, strong and weak, respectively. It also catches that attraction of the insect to trials compounds is more in lightness conditions (p<0.05). It was also found that mating insects more than virgin insects were significantly attracted to trialed compounds (p<0.05). In all trials, the same results obtained with both methods wind tunnel and olfactometer. So according to the results of this research, one of the reasons for attracting clearwing moth is phthalic acid volatile compound in willow and particularly in fertiled insect for oviposition. Therefore, can be investigated the phthalic acid substance to provide bait trap to control the clearwing moth, P, diaphana.