Since 2013, the process of pricing of innovative drugs by the French National Health Insurance has considered both cost-effectiveness and budget impact. CAR-T cell therapies were first subject to economic evaluation from 2019 in France. We aim to describe the process and results of the economic evaluation of tisagenlecleucel and axicabtagene ciloleucel as well as the challenges these evaluations raised. Evaluations submitted by the firms were reviewed by HAS and submitted to the Committee of Economic Evaluation and Public Health (CEESP). The CEESP issued opinions related to: (1) the methodological quality of economic evidence and, (2) the cost-effectiveness and budget impact of the drugs. The CEESP invalidated the estimated incremental cost-utility ratios (ICUR) of tisagenlecleucel due to the insufficient clinical evidence and methodological quality to extrapolate the long-term progression of the disease after treatment and compare tisagenlecleucel with alternatives. The CEESP concluded that tisagenlecleucel was not proven cost-effective. The estimated ICUR of axicabtagene ciloleucel at €114,509/QALY vs. chemotherapies was associated with an acceptable level of methodological quality despite being based on a weak indirect comparison and limited data on quality of life. The CEESP considered axicabtagene ciloleucel ICUR to be “very high” and questioned the societal/community willingness-to-pay of the claimed price. The primary source of uncertainty surrounding the ICUR estimates of both drugs was the lack of hindsight on effectiveness. The economic evaluation of CAR-T cell therapies highlights the risk of inefficient resource allocation driven by limited clinical data. It calls for payment schemes accounting for this risk and effective collection of post-marketing data.