2 Thes. 1:8-10 (ESV)
in flaming fire, inflicting vengeance on those who do not know God and on those who do not obey the gospel of our Lord Jesus.  They will suffer the punishment of eternal destruction, away from the presence of the Lord and from the glory of his might,  when he comes on that day to be glorified in his saints, and to be marveled at among all who have believed, because our testimony to you was believed.
Wow! There is a lot to chew on in these verses: God inflicting vengeance in flaming fire, what it means to know God, and “obey” the gospel of our Lord Jesus Christ, and what it means to suffer punishment away from the presence of the Lord, and from the glory of his might.
In short, the question is: is there a hell? People don’t like believing in Hell. I’m not sure I like believing in it. Hell is hell. People try to get rid of it anyway possible. Possibly the most popular is to downplay the flaming fires, and talk of it as a mere separation from God, drawing off of this being away from the Lord. But it does not say that you are separated from God. It says you are away from the presence of the Lord, and from the glory of his might, that is the forgiveness of sins in Jesus Christ who is Lord. When we are separated from the presence of Jesus Christ by whose blood we are sanctified to stand in the presence of God, we meet with God’s eternal wrath, His punishment for our sin. Yes God is active in Hell, punishing, inflicting vengeance on those who do not know Him, and do not “obey” his God.
I put obey in quotations, I could just as well put know in quotations. Neither really satisfies the meaning of the Greek. To know God is more than to know that he exists or know his name. The knowledge spoken of here only comes through faith, it is a fear, love and trust in God akin to that a child might have for his father. Most of us don’t know president Obama, though we know of him. We know our fathers. We have an intimate knowledge of our fathers. And the word obey here, might be better translated listen to the gospel of our Lord. The distinction is being made between those who hear the gospel, and reject it, and those who hear it and trust it. There really isn’t anything in the Gospel to obey. How do you obey Christ crucified? How do you obey “your sins are forgiven”? The Greek is merely an intensification of the word to hear. Quite literally it is a hyper hearing. We might translate that listen, as in trust what is said is true. The Gospel says Jesus Christ died for you, he forgives your sins. And with that forgiveness we escape the vengeance of God, and come to know Him as our Father.