Do monsters despawn?

[hollowleviathan]

Throwing stuff at them probably slows you down more than them.

@Mr X: Boo.

[DemonGhoul]

Some of the monsters I believe will wander aimless (like the one in the refinery), others are scripted to appear and walk down certain paths after you gain certain objects (ie. storage room).

[Hunter of Shadows]

Some of the monsters I believe will wander aimless (like the one in the refinery), others are scripted to appear and walk down certain paths after you gain certain objects (ie. storage room).

No the one in the refinery disappears a few moments later if you don't get it's attention in any way

[Dragslo]

They are fast like ninjas...it gives you a feeling they vanish when they walk away, then I try to ''find'' them to make sure where they actually went. I have few times stalked a monster to see how long he'd walk without noticing me....call me crazy!

[gandalf91]

Yes, ~95% of them despawn if you hide far enough away from them. If you stick nearby or catch their attention, they will not despawn. The only exceptions I know are:

Spoiler below!

The brute in the sewer and the grunt(s) (1 - 3) that capture you in the Chancel.