In this work, a research has been carried out into the electronic properties of nanostructured graphene. We focus our attention on trapped states of the proposed systems such as spherical and toroidal graphene quantum dots. Using a continuum model, by solving the Dirac-Weyl equation, and applying periodic boundary conditions of two types, i.e. either with zigzag-edges only, or with both armchair-and zigzag-edges, we obtain analytical results for energy levels yielding self-similar energy bands located subsequently one after another on the energy scale. Only for toroidal quantum dots (owing to the lack of curvature) the distribution of electron density is similar to Bohr atomic orbitals. However, although the quasi-zero-energy band exists for both spherical and toroidal quantum dots, no electron density is present on this band for the toroidal quantum dot. This causes the formation of a pseudogap between the hole and electron bands, because of the absence of the electron density at the quantum dot center, like in the case of an ordinary atom. Conversely, the confinement of the charge-carrier density is observed for both geometries of graphene quantum dots.