Per my comment, it depends who you ask.

If you ask the Oxford English Dictionary, pansexuals are a subset of bisexuals.

bisexual, adjective: sexually or romantically attracted to people of more than one sex or gender

pansexual, adjective: sexually or romantically attracted to people without regard to their sex or gender

If you ask Wiktionary, bisexuals and pansexuals are two non overlapping sets of people (though see the usage notes).

bisexual, adjective: sexually attracted to both opposite-sex and same-sex individuals

pansexual, adjective: someone who is attracted to all types of people regardless of gender or sex