A functionalized cellulose filter, with iminodiacetate chelating units, has been characterized for the uptake of ultratrace Pb(II) (1 to 10–6 mg · –1) with the use of210Pb. The different behaviour in batch and in flow-through experiments has been observed both in the rate of metal uptake, as well as in the relative yield of metal recovery. Flow-through uptake appeared to be a faster process and to occur with higher % yield in the entire range investigated. A radioanalytical method for the determination of Pb(II) in liquid samples (10 to 10–2 mg · –1) has been developed, based on the measurement of the210Pb activity exchanged between a iminodiacetic acid filter loaded with210Pb and the solution under analysis. Results and interferences are considered and discussed.