Functional Near Infrared Spectroscopy has been used to investigate changes in cerebral hemodynamics induced by hypercapnia challenges, such as carbon dioxide CO2 inhalation and breath holding. The aim of this study was to investigate CO2 pressure changes dependence of frequency spectrum of cerebral hemodynamic oscillations during breath holding task. Measurements of the relative changes in concentration of deoxy-hemoglobin ([Hb]) and oxy-hemoglobin ([HbO(2)]) are performed on nine healthy subjects during three breath holdings of 30 seconds (s.) interleaved with 90 s. of normal breathing. Power spectra are computed by continuous wavelet transform and averaged for normal and hold episodes. The percent change values between hold and normal episodes are given for frequency peaks at (0.035 Hz), where a 17% higher increase was observed for PC of [Hb] on the right side compared to left side,while this value was at 64.8% for [HbO(2)]. Similarly, for a peak at 0.11 Hz; these values were 54.5% and 9.5% for [Hb] and [HbO(2)] PCs, respectively. The smallest changes were observed for breathing freq. range (around 0.2 Hz) where the values are -72% and 55.8% for [Hb] and [HbO(2)], respectively.