The current study focuses on the measurement of OH* radicals for a laminar premixed hydrogen flame and the interpretation of their intensities and assessment of their use as a plausible flame marker. A spherically expanding flame is studied in a constant volume chamber with the application of high-speed chemiluminescence to identify OH* radicals. The temporal evolution of OH* was investigated as a function of pressures and temperatures, thereby providing insights in their dynamic evolution under varied thermodynamic conditions.