The motional behavior of complex phthaiates has been investigated in order to study the structural effect of the molecular framework upon the dynamic and rheological properties. Coefficients of selfdiffusion and viscosity of dimethyl phthalate (DMP), diethyl phthalate (DEP), dibutyl phthalate (DBP), diamyl phthalate (DAP), dthexyl phthalate (DHP), dioctyl phthaiate (DOP), dinonyl phthalate (DNP) and di-n-decyl phthalate (DDP) have been measured as function of temperature from 20 to 90 Β°C. With a view to accentuate the effect of structural changes in alkyl side chain we examined the transport properties of phthalate esters PE with branching in the aikyl chain (bis(2-methylethyi) phthalate (DIBP), bis(2-ethylhexyl) phthaiate (DEHP), bis(6-methylheptyl) phthaiate (DIOP)). The role of the aromatic ring was studied by comparing of PE viscosity with their analogs derived from cyclohexane. We distinguished three factors effecting the motional behavior of PE: molecular mass (MM), structure and chemical nature of functional groups. We fred out that the MM indirectly characterizes geometry and structure of the moving molecule and that the dominant influences are the structure and chemical nature of the sidechain.