There has been shown an inhibiting effect of ethereal oils Lavandula vera and Salvia sclaria in the mode of arometherapy (ART) on the growth of cells of myeloma Sp 2/0 Ag14 that is expressed in inhibition of development of ascites in mice of line BALB/c and an essential increase in their lifespan. There has also been revealed a correcting influence of ART on the profile of C3 complement system key component spontaneous hydrolysis in the process of blood serum incubation in individuals with neoplasms (breast cancer, Hodgkin's lymphoma and non-Hodgkin's lymphoma) and in patients of cancer risk group (diffuse mastopathy). Furthermore, the observed abrupt surges in the level of С3(Н2О)-conformational form of C3 in the blood serum of oncopatients disappeared after the course of ART or became less expressed compared to the screening group.