In this work, the group contribution approach has been used in combination with the linear isotherm regularity (LIR) equation of state to estimate pvT properties of primary, secondary and tertiary alcohols, ketones and 1-carboxylic acid. In addition, the isothermal compressibility and thermal expansion coefficient of these compounds have been predicted. We assume each of these organic compounds as a hypothetical mixture of methyl, methylene and a functional group, in which the interaction potential of each pair is assumed to be the average effective pair potential. Then, the LIR equation of state (EOS) has been extended to such a hypothetical mixture. Three basic compounds, namely propane, n-butane and cyclohexane, are used to obtain the contribution of methyl and methylene groups in the EOS parameters and also other appropriate compounds are used to obtain the contribution of the functional groups, such as: 1-pentanol for the contribution of -CH2OH, 2-pentanol for the contribution of > CHOH, 2-methyl-2-propanol (t-BuOH) for the contribution of - COH, 2-pentanon for the contribution of > C=O and 1-pentanoic acid for the contribution of -COOH groups. The calculated EOS parameters' along with the modified EOS are then used to calculate the density of different compounds at different pressures and temperatures with the average percentage error less than 1.2. Also, the thermal expansion coefficient at different temperatures and isothermal compressibility at different pressures are calculated for some hydrocarbons with absolute percent deviation less than 1.0. (c) 2005 Elsevier B.V. All rights reserved.