In an adaptive cruise control (ACC) system with object detection system interaction, capable of executing a vehicle speed holding mode, a constant-speed control mode, and a following control mode, a lane-change detector is provided to detect the presence or absence of a driver's intention for a lane change by the host vehicle. An ACC unit executes the vehicle speed holding mode during which the host vehicle's speed is restricted until such time that a predetermined holding time has expired from a time when the object detection system loses the preceding vehicle during the following control mode, and thereafter executes the constant-speed control mode during which the host vehicle's speed is automatically accelerated up to a set speed. The ACC unit releases the vehicle speed holding mode, in presence of the driver's intention for the lane change when the object detection system loses the preceding vehicle during the following control mode.