[cnvogel]

Look closely, the '165 is a little different, both in functionality and pinout. You'll not be able to swap in one for the other. -- But yes, both are parallel in, serial in/out shift registers.

http://www.nxp.com/documents/data_sheet/HEF4021B.pdf http://www.nxp.com/documents/data_sheet/74HC_HCT165.pdf (pinout for LS is the same)