X-Ray single crystal study, molecular mechanics calculations and quantumchemical calculations of the static nonlinear optical (NLO) polarizabilities (β) were performed for a large series of dicyanovinylaromatic derivatives in order to make conclusions about the relationship between their molecular geometry, crystal structure and NLO properties. For some compounds studied EFISH measurements of the P values in solutions were made and good correlation was found between the calculated and experimental values. X-Ray data and optimal molecular associate calculations revealed the factors responsible for formation of centric/acentric crystal structures. This approach might be useful for prediction of possible crystal structures for simple organic chromophores. In the series studied only three acentric crystal structures were found, and in agreement with their molecular, electronic and crystal packing characteristics all were found to be active in second harmonic generation (SHG) in the solid state. For the known NLO crystal of dicyanovinylanisole (DIVA), a high-resolution low-temperature (153K) multipole X-ray diffraction analysis of the electron density distribution has been performed, and these data were used for an estimation of the molecular dipole moment and p values directly from the X-ray diffraction data.