CO2-expanded solvents have been investigated as media for chemical reactions, separation, and materials processing. The tunability Of CO2-expanded fluorinated solvents was examined by two complementary approaches: solvatochromic characterization, which elucidates specific solute/ solvent interactions, and Hansen solubility parameter estimation, which describes bulk solvent properties. The pi* (dipolarity/polarizability) Of CO2-expanded ethoxynonafluorobutane (ENB), as determined from solvatochromic measurements, decreased with increasing CO2 expansion pressure, in agreement with its volume expansion behavior. Analogous to cosolvent tuning in supercritical fluids, the solvent strength of ENB was manipulated with the addition of strong hydrogen-bond-accepting and -donating cosolvents, 2,2,2-trifluoroethanol (TFE; alpha = 1.51) and N-methyl-2-pyrrolidinone (NMP; beta = 0.78), respectively. The Hansen solubility parameters of ENB and CO2-expanded ENB (at 8-20 bar) were estimated from fluorous/organic miscibility studies. The experimental Hansen solubility parameters were used to guide the further selection of immiscible organofluorous pairs that become a homogeneous mixture under mild CO2 pressure.