HD.31 - prototype with Wright Cyclone C7BA1 radial engines (one built)
HD.32 - prototype with Pratt & Whitney R-1830 radial engines. (
two built)
HD.321 - prototype with Wright Cyclone 982 engines and single fin. (
two converted from HD.32 by replacing twin fins with a single central and two small auxiliary fins)
HD.324 - turboprop version with Rolls-Royce Dart engines. (
not built)
HD.33
HD.331 - projected militarised version for use as troop transport or air ambulance. (
not built)
HD.34 - aerial survey version for IGN. (
eight built)  Retractable, offset nosewheel.

HD.35 - a proposed anti-submarine variant for the French Navy, not built.

HD.37 - a proposed car-ferry version, not built.
HD.31 - prototype with Wright Cyclone C7BA1 radial engines (one built)
HD.32 - prototype with Pratt & Whitney R-1830 radial engines. (two built)
HD.321 - prototype with Wright Cyclone 982 engines and single fin. (two converted from HD.32 by replacing twin fins with a single central and two small auxiliary fins)
HD.324 - turboprop version with Rolls-Royce Dart engines. (not built)
HD.33
HD.331 - projected militarised version for use as troop transport or air ambulance. (not built)
HD.34 - aerial survey version for IGN. (eight built)  Retractable, offset nosewheel.
HD.35 - a proposed anti-submarine variant for the French Navy, not built.
HD.37 - a proposed car-ferry version, not built.
Hurel-Dubois HD.31