Radius determination of Cepheids belonging to Type II is presented. Light and radial velocity curves collected from the literature were analyzed with the Baade-Wesselink method. Optical color indices (usually B - V, or V - R when the former was not available) were used to separate the radius and surface brightness variation. The analysis resulted in stellar radii which are in good agreement with other recent results based on infrared photometry (except for AU Peg and κ Pav). The majority of field Type II Cepheids occupy the same range on the period-radius diagram as the globular cluster Cepheids. It is shown, however, that there is a subgroup among Type II Cepheids which contains stars that are significantly larger and probably more luminous than other Type II Cepheids. These peculiar stars are in fact very similar to Pop I (Classical) Cepheids in their size and metallicity, but they lie at higher galactic latitudes. It is not clear whether these are young supergiants indeed, or older low mass stars that had unique evolutions. More contemporaneous photometric and spectroscopic data would be necessary to draw any reliable statistical conclusion.