A vehicle air-conditioning system has an evaporator for receiving air discharged into a casing of the system and changing the air to a cold air flow that can flow rearward, and a heater for selectively receiving at least a portion of the cold air flow and heating such portion to a warm air flow. The system includes partition means for directing the warm air flow to permit mixing of the warm air flow and the remaining cold air flow that bypasses the heater. The partition means includes a top end portion and guide means for downwardly directing the cold, warm, or the mixed cold and warm air which has flowed beyond the top end portion for blowing-out such air out of the system. The top end portion defines a surface having a streamlined or curved configuration along which the cold, warm, or mixed cold and warm air can flow.