**Abstract**

We investigate a planar heterostructures based on gapless graphene and its gap modifications such as a single single heterojunction, a quantum well, and a superlattice. We focus on electron properties of these heterostructures within the envelope wave functions. A new phenomena such as valley-polarized currents along the heterojunction and a pseudospin splitting of an energy spectrum in quantum wells are predicted.

**Keywords**: Graphene, planar heterostructures, pseudospin splitting, interface states, minibands.
