We present a general method to obtain well shaped cavities for treating solvation within the polarizable continuum model (PCM). The cavities are built with Connolly's molecular surface program MSROLL, that allows easy evaluation of all the critical parameters involved in present day PCM technology. The procedure basically works in adapting the isodensity of the solutes at different threshold values. The important features to realize are, that on the one hand there is no uniform threshold value applicable for a reliable description of the solvation effect, and that on the other hand, there are two types of characteristic points to be found when plotting Delta G(el) versus isodensity threshold value of the solute, which are, a minimum for neutral and anionic molecules, or a shoulder for cationic molecules. Taking the respective cavity dimensions at these characteristic points, the experimental values of Delta G(solv) are modeled within chemical accuracy and thus a true ab initio treatment of any arbitrary chemical system should be conceivable within this so-called isodensity adapted polarizable continuum model (IDAPCM).