Potassium iron(III) hexacyanoferrate(II) (K/Fe-Fe(CN)(6)) supported on wood chips (WC) was prepared and its Cs uptake in seawater was measured under batch agitation. The Cs-uptake behavior of this adsorbent was compared with that of K/Fe-Fe(CN)(6) supported on activated carbon (AC), which had already been published. Applying the Elovich equation, both the WC and AC adsorbents showed a similar time-dependence for Cs adsorption reaction, suggesting the same size of K/Fe-Fe(CN)(6) particles for Cs diffusion. From the Cs-adsorption isotherm (298 K), the maximum Cs uptake per unit mole of Fe(CN)(6) supported on WC (0.423 mol/mol-Fe(CN)(6)(-1)) was 7-fold larger than that on AC (0.060 mol/mol-Fe(CN)(6)(-1)): this difference in the Cs uptake should be ascribed to that K/Fe-Fe(CN)(6) particles being partially filled into rather large macropores of WC, whereas narrow macropores in AC were blocked by the K/Fe-Fe(CN)(6). The Cs-distribution coefficient, K-d for K/Fe-Fe(CN)(6)-on-WC is larger than that for K/Fe-Fe(CN)(6)-on-AC when the equilibrium Cs concentration in solution is high.