I want to ask if someone is there. Can both terms be used to ask if a person is there/are you there? いますか or いるの?
I assume what you are asking is "どなたか/誰か + いますか?/いるの?" construction.
どなたか/誰か + いますか?
means you want to get the reply from someone if they are staying there.
So, if someone is replying, it might relieve you.
どなたか/誰か + いるの?
means you are wondering if someone is there since it is unlikely/no sign someone is staying there. So, if someone is replying, it might surprise you.