If my new neighbors told me that my deck was on their property, what can I do?
Question Details: I bought the house 22 years ago and that deck was there already. Would this be considered as adverse possession or would I have to take it down?
It would not be adverse possession if you thought it was your land: advese possession, as the term implies, is "adverse" or hostile--it requires that you know the land belongs to someone else and are actively trying to assert rights over another's land.
IF the neighbors are correct, they can require you to move or take down the deck: you can't intrude on their property. If you refused to do so voluntarily, they could sue you to make you do this. But you don't need to take them at face value: have your land resurveyed. If your survey agrees, you probably should remove the deck if they want you to, to avoid a likely losing litigation. If your survey shows it is your land, you may wish to fight the matter in court, if necessary.