A downhole motor includes a bearing assembly (100) having a mandrel (10) rotatable within a cylindrical housing (20), with the mandrel co-rotatably engaging the rotor (120) of a concentric rotary drive system (110) incorporating an arrangement of housing-mounted gates (130) pivotably deflectable by rotor lobes (124) as the rotor rotates in response to fluid flow through an annular space (40) between the rotor and the housing, building up pressure in longitudinal chambers (140) formed between adjacent gates and lobes and thus inducing rotation of the mandrel. Preferably, the drive system is coupled directly to the bearing assembly, without need for a connecting driveshaft, and with the housing incorporating a bent sub (210) positioned above the drive section. Alternatively, a bent sub may be positioned below the drive system in conjunction with the use of a driveshaft to connect the drive system to the bearing section, in order to position the bend as close as possible to the bit.