Current models of s-nucleosynthesis in massive stars ($Msim15 M_{odot}$ to $sim 30 M_{odot}$) are able to reproduce some main features of the abundance distributions of heavy isotopes in the solar system, at least in the $Asim 60-90$ mass range. The efficiency of the process and the above specified mass range for the s-nuclei are still heavily uncertain due to both nuclear reaction rates and stellar models uncertainties. A series of s-process simulations with stellar models in the $15-30 M_{odot}$ (mass at ZAMS) and metallicity $Z=0.02$ mass have been performed to analyse the impact of the overshooting model used on the s-process yields. As in a previous exploratory work performed with stellar models having $M_{ZAMS}=25 M_{odot}$ and $Z=0.02$, enhancements factors in the range 2-5 are found in the final s-process efficiency when overshooting is inserted in the models.
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