Groundwater of Wadi Nu'man (30 km southeast of Mecca city) of high radon-222 (Rn-222) content, emanated directly from the bed rock into the water reservoir, has been analyzed for lead-210 (Pb-210) and polonium-210 (Po-210), the comparatively long-lived Rn-222 progenies, to study the effect of the continuous Rn-222 emanation on the accumulation of both radionuclides in this water. Emanation of Rn-222 directly from rock to water may be affected seasonally by atmospheric temperature and pressure; therefore, Rn-222 and Rn-222 progenies were reanalyzed in seasonal samples of the same wells. The obtained results showed Pb-210 and Po-210 activity levels ranging from <6 to 29.9 and from 0.6 to 18.2 mBq/L, respectively, which was far below the recorded level of their parent radionuclide 222Rn (10.9-99.7Bq/L). The data have been discussed in detail.