A novel maize variety designated PHHMD and seed, plants and plant parts thereof. Methods for producing a maize plant that comprise crossing maize variety PHHMD with another maize plant. Methods for producing a maize plant containing in its genetic material one or more traits introgressed into PHHMD through backcross conversion and/or transformation, and to the maize seed, plant and plant part produced thereby. Hybrid maize seed, plant or plant part produced by crossing the variety PHHMD or a trait conversion of PHHMD with another maize variety. Inbred maize varieties derived from maize variety PHHMD, methods for producing other inbred maize varieties derived from maize variety PHHMD and the inbred maize varieties and their parts derived by the use of those methods.