Ortho-positronium (o-Ps) lifetime in alkanes and alcohols was measured in a broad range of temperatures and the results were compared with calculations in the framework of a standard bubble model. The lifetimes as a function of temperature above the melting point are almost identical for all alkanes. Assuming the potential well depth of 1eV, the best fit of a model curve to the experimental data is obtained for surface tension increased by factor of about 1.4–1.6 comparing to flat surface. If the well depth is larger, this correcting coefficient should be larger too. The difference of decay constants in alcohol and alkane of the same chain length at a given surface tension is small; it can be ascribed to the traces of radiation chemical reactions, or to nonequal potential well depths.