A novel inbred maize line designated PHADP and seed, plants and plant parts thereof. Methods for producing a maize plant that comprise crossing inbred maize line PHADP with another maize plant. Methods for producing a maize plant containing in its genetic material one or more traits introgressed into PHADP 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 inbred line PHADP or an introgressed trait conversion of PHADP with another maize line. Inbred maize lines derived from inbred maize line PHADP, methods for producing other inbred maize lines derived from inbred maize line PHADP and the inbred maize lines and their parts derived by the use of those methods.