diff --git a/Lib/xml/etree/ElementTree.py b/Lib/xml/etree/ElementTree.py
--- a/Lib/xml/etree/ElementTree.py
+++ b/Lib/xml/etree/ElementTree.py
@@ -549,10 +549,29 @@
     """
     def __init__(self, element=None, file=None):
         # assert element is None or iselement(element)
+        self._children = []  # comments and processing instructions only
         self._root = element # first node
         if file:
             self.parse(file)
 
+    def append(self, element):
+        """Add a Comment or ProcessingInstruction *element* to appear before
+           the ElementTree's root element.
+
+        """
+        tag = getattr(element, 'tag', None)
+        if not (tag is Comment or tag is PI):
+            raise TypeError('expected a Comment or ProcessingInstruction')
+        self._children.append(element)
+
+    def remove(self, element):
+        """Remove matching element based on element identity.
+
+        ValueError is raised if a matching element could not be found.
+
+        """
+        self._children.remove(subelement)
+
     def getroot(self):
         """Return root element of this tree."""
         return self._root
@@ -765,6 +784,13 @@
                     declared_encoding = locale.getpreferredencoding()
                 write("<?xml version='1.0' encoding='%s'?>\n" % (
                     declared_encoding,))
+                for elem in self._children:
+                    tag = elem.tag
+                    text = elem.text
+                    if tag is Comment:
+                        write("<!--%s-->" % text)
+                    elif tag is ProcessingInstruction:
+                        write("<?%s?>" % text)
             if method == "text":
                 _serialize_text(write, self._root)
             else: