Supercritical fluid phase equilibrium behavior of binary and ternary systems has been ascertained for separation of three pairs of aromatic chemicals having close molecular weights, namely, decalin + tetralin, anisaldehyde + anisic acid, and menthol + thymol. The respective fluid-liquid equilibrium and solidfluid equilibrium phase compositions have been measured over a pressure range of 55-160 bar and temperature range of 323-373 K with carbon dioxide. The selectivity of separation is higher at lower temperature but increases with pressure up to a certain pressure beyond which it decreases. Apparent selectivities for the tetralin + decalin system from the binary data are comparable to experimental selectivities from the ternary data. Binary results may be used for assessing the selectivity of separation for systems having minimal chemical interaction. Supercritical carbon dioxide is a selective solvent for all three binary pairs of aromatic compounds studied.