A diffuser for an air freshener product includes a casing having front and rear casing portions fastened together. A neck opening is formed inside said casing into which a neck of an air freshener reservoir is secured. A wick extends from the neck of the air freshener reservoir into the interior of the casing. The casing has openings in the front and back through which air flows. An air flow control element is provided in the casing to permit a user to change the air flow to the wick and thereby vary the air freshener product dispersed into the air. The air flow control element has a knob extending from the casing that is operable by the user. The rear portion of the casing has a fastener to which is attached a clip having two extended flexible arms that engage into a vent grill of an air conditioner system of a vehicle. The clip is securable in the fastener at positions oriented 90 degrees from one another to enable the clip to be fastened to vertically or horizontally oriented air conditioner grill slats.