Density functional calculations of hydrocarbon prismanes C2nH2n (where n = 3–10) and their substituted derivatives are carried out to analyze their structures, binding energies and electronic properties. Five substituting radicals (F, Cl, CH3, OH, NO2) are considered. The results indicate the different behavior of the prismanes by substitutions of hydrogen atoms with different radicals. Effective repulsion of substituting radicals on the pentaprismane cage is detected. The dependences of binding energies on number of substituted radicals demonstrate increasing or decreasing trends for different radicals. HOMO-LUMO gaps are slightly changed by substituting doping. All substituting reactions are found to be endothermal. Fluorination is more energetically feasible than other considered reactions.