diff --git a/nested-sets.cabal b/nested-sets.cabal
--- a/nested-sets.cabal
+++ b/nested-sets.cabal
@@ -1,5 +1,5 @@
 name: nested-sets
-version: 0.0.1.0
+version: 0.0.1.1
 cabal-version: >=1.10
 build-type: Simple
 license: GPL-3
@@ -12,6 +12,7 @@
              Supported functionality includes:
              .
                  * conversion from and to Forest structure from Data.Tree;
+             .
                  * position support with moving to parent, sibling and child nodes.
 homepage:
 stability: alpha
diff --git a/src/lib/Data/NestedSet.hs b/src/lib/Data/NestedSet.hs
--- a/src/lib/Data/NestedSet.hs
+++ b/src/lib/Data/NestedSet.hs
@@ -9,6 +9,8 @@
     nestedSetsParentPosition,
     nestedSetsFirstChildPosition,
     nestedSetsPositionValue,
+    nestedSetsPositionSetValue,
+    isNestedSetsPositionParent,
     ) where
 
 import Data.Tree (Forest, Tree (..), rootLabel, subForest)
@@ -50,7 +52,7 @@
 nestedSetsNextSiblingPosition [] _ = Nothing
 nestedSetsNextSiblingPosition (first : ds) pos
     | position first == pos = firstPositionOf ds
-    | isPositionParent (position first) pos = nestedSetsNextSiblingPosition (children first) pos
+    | isNestedSetsPositionParent (position first) pos = nestedSetsNextSiblingPosition (children first) pos
     | otherwise = nestedSetsNextSiblingPosition ds pos
     where firstPositionOf [] = Nothing
           firstPositionOf (firstSet : _) = Just . position $ firstSet
@@ -59,34 +61,43 @@
 nestedSetsParentPosition :: NestedSets a -> Position -> Maybe Position
 nestedSetsParentPosition [] _ = Nothing
 nestedSetsParentPosition (firstSet:ds) pos
-    | isPositionParent (position firstSet) pos = descendToChildren firstSet
+    | isNestedSetsPositionParent (position firstSet) pos = descendToChildren firstSet
     | otherwise = nestedSetsParentPosition ds pos
     where findParentPos [] _ = Nothing
           findParentPos (x : xs) currentParent
             | position x == pos = Just . position $ currentParent
-            | isPositionParent (position x) pos = descendToChildren x
+            | isNestedSetsPositionParent (position x) pos = descendToChildren x
             | otherwise = findParentPos xs currentParent
           descendToChildren set = findParentPos (children set) set
 
 -- | Advance the position to the first child node.
 nestedSetsFirstChildPosition :: NestedSets a -> Position -> Maybe Position
-nestedSetsFirstChildPosition [] _ = Nothing
-nestedSetsFirstChildPosition (first : ds) pos
-    | position first == pos = firstPosition . children $ first
-    | isPositionParent (position first) pos = nestedSetsFirstChildPosition (children first) pos
-    | otherwise = nestedSetsFirstChildPosition ds pos
-    where firstPosition [] = Nothing
-          firstPosition (x : _) = Just . position $ x
+nestedSetsFirstChildPosition sets pos = firstPosition . (fmap children) $ findPosition sets pos
+    where firstPosition Nothing = Nothing
+          firstPosition (Just []) = Nothing
+          firstPosition (Just (x : _)) = Just . position $ x
 
 -- | Retrieve the value for the given 'Position'.
 nestedSetsPositionValue :: NestedSets a -> Position -> Maybe a
-nestedSetsPositionValue [] _ = Nothing
-nestedSetsPositionValue (first : ds) pos
-    | position first == pos = Just . content $ first
-    | isPositionParent (position first) pos = nestedSetsPositionValue (children first) pos
-    | otherwise = nestedSetsPositionValue ds pos
+nestedSetsPositionValue sets pos = fmap content $ findPosition sets pos
 
+-- | Set value for the 'Position' on the given nested set.
+--   Does not modify the given 'NestedSets' if the 'Position' cannot be found.
+nestedSetsPositionSetValue :: NestedSets a -> Position -> a -> NestedSets a
+nestedSetsPositionSetValue [] _ _ = []
+nestedSetsPositionSetValue (first : ds) pos value
+    | position first == pos = (first {content = value}) : ds
+    | isNestedSetsPositionParent (position first) pos = (first {children = nestedSetsPositionSetValue (children first) pos value }) : ds
+    | otherwise = first:(nestedSetsPositionSetValue ds pos value)
 
-isPositionParent :: Position -> Position -> Bool
-isPositionParent (parentL, parentR) (childL, childR) = parentL < childL && parentR > childR
+isNestedSetsPositionParent :: Position -> Position -> Bool
+isNestedSetsPositionParent (parentL, parentR) (childL, childR) = parentL < childL && parentR > childR
+
+
+findPosition :: NestedSets a -> Position -> Maybe (NestedSetsNode a)
+findPosition [] _ = Nothing
+findPosition (first : ds) pos
+    | position first == pos = Just first
+    | isNestedSetsPositionParent (position first) pos = findPosition (children first) pos
+    | otherwise = findPosition ds pos