diff --git a/Control/ContStuff.hs b/Control/ContStuff.hs
--- a/Control/ContStuff.hs
+++ b/Control/ContStuff.hs
@@ -22,7 +22,7 @@
     -- ** Choice/nondeterminism
     ChoiceT(..), runChoiceT, findFirst, findAll, listChoiceT, listA,
     -- ** Exceptions
-    EitherT(..), runEitherT, evalEitherT,
+    EitherT(..), runEitherT, evalEitherT, modifyEitherT,
     -- ** State
     StateT(..), runStateT, evalStateT, execStateT,
     -- ** Writer monads
@@ -340,6 +340,12 @@
 evalEitherT (EitherT c) = c (pure . Right) (pure . Left)
 
 
+-- | Modify the result of an 'EitherT' computation along the way.
+
+modifyEitherT :: Functor m => (r -> r) -> EitherT r e m ()
+modifyEitherT f = EitherT $ \k _ -> fmap f (k ())
+
+
 ---------
 -- IdT --
 ---------
@@ -674,6 +680,8 @@
   type Base (ChoiceT r i m) a = Base m a; base = lift . base
 instance (LiftBase m a, Monad m) => LiftBase (ContT r m) a where
   type Base (ContT r m) a = Base m a; base = lift . base
+instance (LiftBase m a, Monad m) => LiftBase (EitherT r e m) a where
+  type Base (EitherT r e m) a = Base m a; base = lift . base
 instance (LiftBase m a, Monad m) => LiftBase (StateT r s m) a where
   type Base (StateT r s m) a = Base m a; base = lift . base
 
@@ -706,6 +714,12 @@
 
 instance (Monad m, Stateful m) => Stateful (ContT r m) where
   type StateOf (ContT r m) = StateOf m
+  get = lift get
+  put = lift . put
+  putLazy = lift . putLazy
+
+instance (Monad m, Stateful m) => Stateful (EitherT r e m) where
+  type StateOf (EitherT r e m) = StateOf m
   get = lift get
   put = lift . put
   putLazy = lift . putLazy
diff --git a/contstuff.cabal b/contstuff.cabal
--- a/contstuff.cabal
+++ b/contstuff.cabal
@@ -1,5 +1,5 @@
 Name:          contstuff
-Version:       0.3.0
+Version:       0.3.1
 Category:      Control, Monads
 Synopsis:      Easy to use CPS-based monads
 Maintainer:    Ertugrul Söylemez <es@ertes.de>