Essential oils are considered as very complex natural mixtures containing numerous components at quite various concentrations. Lythrum salicaria has not been previously subjected to examination of its volatile oil. The present study was carried out to evaluate the essential oil composition of the flowering aerial parts of the plant by using conventionally hydro-distillation (HD) and microwave assisted hydro-distillation (MAH) methods along with the aromatic water obtained by hydro-distillation. Components of these three samples were recognized by GC/MS. Identification of components resulted in recognition of 14 (98% oil), 32 (98.4%), and 10 (95.5%) compounds for HD, its hydrolate, and MAH samples, respectively. The predominant constituents in the HD oil were bis (2-ethylhexyl) phthalate (29.2%), n-hexadecanoic acid (22%), and pentacosane (9.5%). The major constituents of the hydrolate were elucidated as 2(4H)-benzofuranone-5,6,7,7a-tetrahydro-4,4,7a-trimethyl (6.4%), neryl acetone (6%), pentanoic acid (5.7%), nonanoic acid (5.6%), and octanoic acid (5.5%). Accordingly, bis (2-ethylhexyl) phthalate (43.2%), methyl-cyclopentane (36.5%), and pentacosane (4.7%) were assessed as the main components of MAH oil. Comparing the three samples compositions, it was concluded that the extraction procedure led to variations in quality and quantity of volatiles. Besides, bis (2-ethylhexyl) phthalate, the common plasticizer, was identified as the main pollutant in both HD and MAH oils. The presence of this substance in the oils provided the evidence of contaminations that was absorbed from water into the plant suggesting GC/MS as a suitable method for its detection in plant materials.