The influence of the input power (IP), puffing rate and neutral pressure on the fuel (hydrogen isotopes) inventory of the WEST and ITER divertors is investigated. For the chosen range of parameters (relatively low temperature at the strike points), the inventory of the WEST divertor evolves as the power 0.2 of the puffing rate and as the power 0.3 of the IP. The inventory at the strike points is highly dominated by ions whereas it is dominated by neutrals in the private zone. Increasing the fuelling rate increases the retention in the private zone and decreases slightly the retention at the strike points. Increasing the IP increases the inventory at the strike points and does not affect much the inventory at the private flux region. The inventory of the ITER divertor is not strongly dependent on the divertor neutral pressure. The inventory increases from 0 Pa to 7 Pa and then decreases slightly from 7 Pa to 10 Pa. After 107 s of continuous exposure, the maximum inventory in the ITER divertor was found to be 14 g. The inventory is not maximum at the strike points due to the high surface temperature of the monoblocks in this region. The maximum accumulation of H in the ITER divertor is below 5 mg per 400 s discharge and below 2 mg per 400 s discharge after 200 discharges.