AIM: To undertake cost-effectiveness and cost-benefit analyses of an intervention to improve oral health in patients presenting with the gingival manifestations of oral lichen planus (OLP). MATERIALS & METHODS: Eighty-two patients were recruited to a 20-week randomized controlled trial. The intervention was personalized plaque control comprising powered tooth brushing and inter-dental cleaning advice. The primary outcome measure was the oral health impact profile (OHIP) with secondary outcomes of pain, plaque index, mucosal disease score and cost-effectiveness. Private cost data and stated willingness-to-pay (WTP) values for treatment were obtained from intervention patients at 20 weeks. RESULTS: Overall, 81% of intervention patients showed improvement in both plaque index and mucosal disease score at 20 weeks compared to 30% of controls that continued with their usual plaque control regimen. All intervention group patients stated a positive WTP value. The mean net value of the treatment was £172 compared to the incremental cost of the treatment estimated at £122.75. The cost-effectiveness analysis resulted in an incremental cost-effectiveness ratio of £13 per OHIP point. CONCLUSIONS: The tailored plaque control programme was more effective than control in treating the gingival manifestations of oral lichen planus. The programme is cost effective for modest values placed on a point on the OHIP scale and patients generally valued the treatment in excess of the cost.