What is another word for someone who listens attentively?

Here are some synonyms for someone who listens attentively:

Formal:

* Attentive

* Heedful

* Mindful

* Observant

* Perceptive

* Thoughtful

Informal:

* Eager listener

* Good listener

* Engaged

* Intrigued

* All ears

* Hanging on every word

The best word to use will depend on the context and the tone you want to convey.