Magnetic interactions in phenylenevinylene-bridged organic radicals are investigated as realistic models of pendant-type ferromagnetic polymers, since several molecules having some types of phenylenevinylene skeletons with phenoxy or nitroxide radicals were recently synthesized and their ferromagnetic characters were also confirmed by experimental works. In the present study, a spin source of NOH nitroxide radical is examined as a model of stable tertiary-butyl nitroxide in this system. According to NOH orientations, it is possible to form hydrogen bond between radical O and vinylene H atoms which may work as additional effects on the ferromagnetic spin coupling. To elucidate this point, density-functional calculations are carried out for both monomers and polymers by using Becke's exchange with Lee-Yang-Parr correlation functional. It is detected that the influence of hydrogen bond is emphasized in polymers by the cooperative interaction arising from one-dimensional network along chain. Implications of the hydrogen-bonding effects are briefly discussed in relation to hydrogen abstraction reactions by nitroxide groups and stabilizations of ferromagnetic polymers by selections of substitution positions of radical groups. Computational results were also compared with available experimental results by Nishide, Tsuchida, and others. Finally, a new proposal for synthesis of thermal and photo-induced organic ferrimagnets is presented.