The adiabatic correction is calculated for a series of 50 typical medium size molecules containing H atoms, most of them for the first time. The effect increases with the size of organic compounds. For this kind of molecules it is found, as a general rule, that the adiabatic correction per electron is an almost constant value, amounting approximately 0.27 x 10(-3) an. (c) 2005 Elsevier B.V. All rights reserved.