This study provides the first information on the subcellular distribution and chemical forms of Cd in the edible seaweed, P. yezoensis. It may accumulate high concentrations of Cd. Under natural conditions, the proportions of Cd in the cell wall, organelle and soluble fractions of P. yezoensis were 52.9%, 15.9% and 31.2%, respectively. As Cd2+ concentrations in the experimental treatments and exposure time increased, the proportion of Cd in the cell wall increased, while the proportion of Cd in the cell organelle and soluble fractions decreased. For all experimental treatments, the largest proportion of Cd was localised in the cell wall and the lowest Cd was in the organelle-containing fraction. Under natural conditions, the largest proportion of Cd was in the 1 M NaCl extractable Cd fraction; however, when exposed to high concentrations of Cd, the highest proportion was extracted by 2% HAC, indicating that it precipitated with phosphate. Chemical forms analysis showed that, under various Cd treatments, most of the Cd was precipitated with phosphate and this was different from those grown in a natural environment in which most of the Cd was extractable by 1 M NaCl. So the tolerance strategy involved in Cd detoxification may include cell wall deposition and formation of precipitates with phosphate.