Using quantile regression, we compare the relationship between CEO founder and CEO age and the performance of new firms in the US. Our empirical evidence shows that issuers led by a CEO founder have a strong positive impact on first-day returns, especially at the intermediate level of underpricing, while underpricing declines as CEO age increases, especially above the 40th percentile, which would not be confirmed by a classical linear regression. This finding suggests that estimating the different quantile effects of a response variable may be more informative than estimating only the average effect of the response variable. In addition, CEO founders exacerbate uncertainty about issuer quality with firm expansion; and in large firms, mature CEOs perform better than young ones in reducing the first trading day return; the mature CEO has a strong negative impact on initial returns only in low-R&D firms, and the CEO founder has a significant positive association with underpricing in R&D-intensive firms. (c) 2025 ASEPUC. Published by EDITUM- Universidad de Murcia. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).