Index: twisted/mail/test/test_imap.py
===================================================================
--- twisted/mail/test/test_imap.py	(revision 35014)
+++ twisted/mail/test/test_imap.py	(working copy)
@@ -885,6 +885,46 @@
                 self.assertEqual(L, expected,
                                   "len(%r) = %r != %r" % (input, L, expected))
 
+
+    def test_IfQuotedString(self):
+        """
+        The strings passed to L{imap4._ifQuotedString} are not tokens, so
+        C{True} should be returned.
+        """
+        inputs = [
+            'some ramdom stuff',
+            '(twisted)',
+            '<twisted>',
+            'twisted@',
+            'twisted,',
+            'twisted;',
+            'twisted:',
+            'twisted\\',
+            'twisted"',
+            'twisted/',
+            '[twisted]',
+            'twisted?',
+            'twisted=',
+        ]
+
+        # Add all the control characters
+        for i in range(33):
+            inputs.append('twiste'+ chr(i) + 'd')
+
+        for i in inputs:
+            self.assertEqual(imap4._ifQuotedString(i), True)
+
+
+    def test_IfTokens(self):
+        """
+        The strings passed to L{imap4._ifQuotedString} are tokens, so
+        C{False} should be returned.
+        """
+        result = imap4._ifQuotedString("I'm.a.token!")
+        self.assertEqual(result, False)
+
+
+
 class SimpleMailbox:
     implements(imap4.IMailboxInfo, imap4.IMailbox, imap4.ICloseableMailbox)
 
@@ -3457,6 +3497,33 @@
             structure)
 
 
+    def test_singlePartDisposition(self):
+        """
+        For some content-disposition parameter values,
+        L{imap4.getBodyStructure} returns quoted-string.
+        """
+        body = 'hello, world'
+        major = 'image'
+        minor = 'jpeg'
+        charset = 'us-ascii'
+        msg = FakeyMessage({
+                'content-type': '%s/%s; charset=%s; x=y' % (
+                    major, minor, charset),
+                'content-disposition': 'attachment; filename=foo (doc).pdf; ' \
+                    'size=bar; creation-date=somedate; ' \
+                    'modification-date=somedate; read-date=somedate',
+                }, (), '', body, 123, None)
+        structure = imap4.getBodyStructure(msg, extended=True)
+        self.assertEqual(
+            [major, minor, ["charset", charset, 'x', 'y'], None,
+             None, None, len(body), None,
+             ['attachment', ['filename', '"foo (doc).pdf"', 'size', 'bar',
+              'creation-date', '"somedate"',
+              'modification-date', '"somedate"',
+              'read-date', '"somedate"']], None, None],
+            structure)
+
+
     def test_textPart(self):
         """
         For a I{text/*} message, the number of lines in the message body are
Index: twisted/mail/imap4.py
===================================================================
--- twisted/mail/imap4.py	(revision 35014)
+++ twisted/mail/imap4.py	(working copy)
@@ -4327,6 +4327,29 @@
             return 1
     return 0
 
+# tspecial in RFC 2045
+_TSPECIALS = r'()<>@,;:\"/[]?='
+def _ifQuotedString(s):
+    """
+    It determines if a string is a token or quoted-string.
+    @see: U{http://www.ietf.org/rfc/rfc2045.txt}
+
+    @type s: C{str}
+    @param s: The string needs to be checked
+
+    @return: True if the string needs quotation marks, False if the
+        string is a token.
+    """
+    if s == '':
+        return True
+    for c in s:
+        # ASCII characters without control characters
+        if c <= '\x20' or c > '\x7f':
+            return True
+        if c in _TSPECIALS:
+            return True
+    return False
+
 def _prepareMailboxName(name):
     name = name.encode('imap4-utf-7')
     if _needsQuote(name):
@@ -4895,6 +4918,11 @@
         Parse a I{Content-Disposition} header into a two-sequence of the
         disposition and a flattened list of its parameters.
 
+        According to RFC2183, the following parameter values will be quoted:
+            1. Values of date parameters
+            2. Values contain only ASCII characters, but including
+               tspecials characters.
+
         @return: C{None} if there is no disposition header value, a C{list} with
             two elements otherwise.
         """
@@ -4904,7 +4932,16 @@
                 disp = (disp[0].lower(), None)
             elif len(disp) > 1:
                 # XXX Poorly tested parser
-                params = [x for param in disp[1:] for x in param.split('=', 1)]
+                date_params = ['creation-date', 'modification-date',
+                               'read-date']
+                params = []
+                for param in disp[1:]:
+                    key, value = param.split('=')
+                    params.append(key)
+                    if key in date_params or _ifQuotedString(value):
+                        params.append(_quote(value))
+                    else:
+                        params.append(value)
                 disp = [disp[0].lower(), params]
             return disp
         else: