Numeric modeling and the PetraSim program with a TOUGH2 deposit simulator have been applied to the evaluation of the viability of seasonal (cyclic) hydrogen storage in a deep aquifer, in the porous rocks of a well-recognized geological structure Suliszewo. The modeling was performed for one injection-and-withdrawal well located on the summit of the structure, under an assumption that the values of the fracturing pressure and capillary entry pressure will not be exceeded. Upconing seems to be the main obstacle in underground hydrogen storage. It was noted that the amount of recovered hydrogen increases in successive withdrawal cycles. It is shown that the management of large amounts of water during hydrogen withdrawal will be a serious environmental issue, important also for the cost-effectiveness of the underground storage. The obtained modeling results indicate that underground hydrogen storage in a deep aquifer may be performed with reasonable parameters of gas recovery. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.