The solubilities of anthracene and carbazole in liquid and supercritical isobutane have been experimentally determined in a static view cell, at temperatures from (367 to 418 K) and pressures from (3.2. to 8.6) MPa. The solubilities of anthracene varied from (7.3 to 51.8) mg of solute per gram of isobutane, whereas those of carbazole were from (1.4 to 9.9) mg of solute per gram of isobutane within the experimental range studied. These differences in solute solubilities have been explained attending to the higher vapor pressures of anthracene and its smaller dipole moment (and so stronger affinity to isobutane). The experimental solubilities have been compared to those of these solutes in propane and CO2. At similar reducer. temperature and pressure conditions, it has been found that solute mole fractions are higher in isobutane than in the other two fluids (3 to 15 times and 160 to 270 times higher than in propane and CO2, respectively). Anthracene and carbazole solubilities in isobutane have been modeled by the Peng-Robinson equation of state. Good fit of the experimental results has been obtained (APD values of 6.7 % for anthracene and 9.7 % for carbazole).