A semiconductor package includes a package substrate, a processor chip mounted on the package substrate, a first stack structure on the package substrate, the first stack structure including a number M of memory chips stacked on the processor chip, and a second stack structure on the package substrate and spaced apart from the processor chip, the second stack structure including a number N of memory chips stacked on the package substrate. A number Q of channels that electrically connect the memory chips of the second stack structure with the processor chip may be greater than a number P of channels that electrically connect the memory chips of the first stack structure with the processor chip, or the number N of memory chips included in the second stack structure may be greater than the number M of memory chips included in the first stack structure.