It's me who AM/IS waiting for you. (Am or is?) This is a complicated question. But the answer follows a simple rule. (1) If you want to answer the question: "Who's there?" or "Who is it?" then you say It's me. Some English speakers will object to this, but they are ignoring reality. See, for example: http://drgrammar.org/frequently-asked-questions#73 (2) If you want to use a sentence in which you add a relative clause, then you can use It is I who am waiting for you (more common in writing) or you can say: It's me who's waiting for you (acceptable in spoken English) Note, however, that English speakers would rarely use such a sentence. We would probably say: I am the one who is waiting for you. The one who is waiting for you is me. We go with what sounds best, and not by Latin grammar. This is what I teach my students. However, not every English speaker agrees. For example, many people object to (1)(It's me) on the basis of "formal grammar." However, the grammar they are talking about is Latin grammar. And forcing English to work like Latin works is misguided. In Latin, all the nouns are inflected and all the verbs are conjugated. In English this is not the case. In English, we go by other things, including word order and what sounds good. "It is I" sounds pompous and stuffy. This is probably why "It is me" (It's me") has been in use since the 16th Century. For additional information, please see: http://english.stackexchange.com/questions/10643/which-one-is-correct-to-say-its-me-or-its-i http://english.stackexchange.com/questions/10643/which-one-is-correct-to-say-its-me-or-its-i http://english.stackexchange.com/questions/68919/it-is-i-who-am-at-fault

"It is I who is waiting for you." First of all, the correct pronoun here is "I," not "me." That's because "I" is NOT the object of the verb "is." You are expressing equivalence, not the target of an action. This is one of these awkward cases. All careful speakers with sensitivity to grammar agree that "It is I" is correct and that "It is me" is incorrect. However, because the pronoun follows the verb, it "feels like" an object, and thus people follow the habit pattern and use the object pronoun. This is so very common that you can't really say it's wrong. Why do I say "is waiting?" I'm a native U.S. speaker but not a grammarian. My intuition is this. Even though "who" follows "I", is NOT referring to "I." It is referring back to "It." Thus, the structure of the sentence is not "I am waiting for you," it is "It is waiting for you."

who is waiting for you is correct

Mina, you can learn all about pronoun rules here: http://m.grammarbook.com/grammar-rules/pronouns.aspx