Can I pour a cement slab onto an existing slab?

Can I pour cement onto an existing slab? Its a patio, so no heavy weight will be on the slab besides normal patio furnature and 2 fibergl post that supports the roof. The patio is 12'X20'. I want to raise it 3 to 4 inches. The existing patio doesn't have a really smooth finish on top that I can tell.