That no study has investigated oral health-related quality of life (OHRQoL) through the transition from adolescence to young adulthood is partly due to no OHRQoL index having been validated in both adult and child populations. Having separate measures for adolescence and young adulthood has meant that the different measures cannot be compared directly. Accordingly, the study objectives were: to determine whether the CPQ11-14 is a valid and reliable OHRQoL measure in young adults and to compare its performance with the OHIP-14 in young adults. A cross-sectional study was undertaken of a convenience sample of 968 young New Zealand adults aged 18-30 years (83.1% female) using RedCap. Two separate measures of OHRQoL were used (the CPQ11-14 and OHIP-14), along with Locker's global oral health item. Internal consistency reliability was high for the CPQ11-14 and the OHIP-14, with Cronbach's alpha scores of .87 and .92, respectively. Mean scale scores were 15.8 (SD = 9.7) for the CPQ11-14 and 24.1 (SD = 10.1) for the OHIP-14. The scale scores were strongly and positively correlated (Pearson's r = .8). Both demonstrated acceptable construct validity, represented by ascending gradients in mean scores across the ordinal response categories of Locker's global oral health item. Ordinal logistic regression modelling of Locker's item showed the CPQ11-14 to have a slightly better fit and explain more variance than the OHIP-14. The CPQ11-14 was valid and reliable in this young adult population. Further epidemiological validation studies should confirm the findings in representative samples.