diff --git a/modoboa/admin/__init__.py b/modoboa/admin/__init__.py
index d331e303b..b46cf5b8f 100644
--- a/modoboa/admin/__init__.py
+++ b/modoboa/admin/__init__.py
@@ -21,6 +21,7 @@ parameters.register_admin("MAILBOX_TYPE", type="list", deflt="maildir",
                           values=[("maildir", "maildir"), ("mbox", "mbox")],
                           help=ugettext_lazy("Mailboxes storage format"))
 parameters.register_admin("MAILDIR_ROOT", type="string", deflt=".maildir",
+                          visible_if="MAILBOX_TYPE=maildir",
                           help=ugettext_lazy("Sub-directory (inside the mailbox) where messages are stored when using the maildir format"))
 parameters.register_admin(
     "PASSWORD_SCHEME", type="list", deflt="md5crypt",
diff --git a/modoboa/admin/templatetags/admin_extras.py b/modoboa/admin/templatetags/admin_extras.py
index 115821911..a5ac79aec 100644
--- a/modoboa/admin/templatetags/admin_extras.py
+++ b/modoboa/admin/templatetags/admin_extras.py
@@ -49,15 +49,15 @@ def settings_menu(selection, user):
          "url" : "extensions/",
          "label" : _("Extensions"),
          "img" : ""},
+        {"name" : "info",
+         "class" : "ajaxlink",
+         "url" : "info/",
+         "label" : _("Information")},
         {"name" : "parameters",
          "class" : "ajaxlink",
          "url" : "parameters/",
          "img" : "",
          "label" : _("Parameters")},
-        {"name" : "info",
-         "class" : "ajaxlink",
-         "url" : "info/",
-         "label" : _("Information")}
         ]
     return render_to_string('common/menu.html', {
             "entries" : entries, 
@@ -201,10 +201,16 @@ def param(app, definition):
     value = definition.has_key("value") \
         and definition["value"] or definition["deflt"]
 
-    result = """<div class='control-group'>
+    extratags = ""
+    if "visible_if" in definition:
+        vfield, vvalue = definition["visible_if"].split("=")
+        extratags = "data-visibility-field='%s.%s' data-visibility-value='%s'" \
+            % (app, vfield, vvalue)
+
+    result = """<div class='control-group'%s>
   <label class="param-label" for="%s">%s</label>
   <div class="param-controls">""" \
-        % (name, definition.has_key("label") and _(definition["label"])
+        % (extratags, name, definition.has_key("label") and _(definition["label"])
            or definition["name"])
     if definition["type"] in ["string", "int"]:
         result += """
diff --git a/modoboa/admin/views.py b/modoboa/admin/views.py
index fef28f6e7..706d9367e 100644
--- a/modoboa/admin/views.py
+++ b/modoboa/admin/views.py
@@ -493,8 +493,9 @@ def viewparameters(request, tplname='admin/parameters.html'):
                       "help" : param_def["help"],
                       "default" : param_def["deflt"],
                       "type" : param_def["type"]}
-            if "values" in param_def.keys():
-                newdef["values"] = param_def["values"]
+            for k in ["values", "visible_if"]:
+                if k in param_def.keys():
+                    newdef[k] = param_def[k]
             tmp["params"] += [newdef]
         gparams += [tmp]
 
diff --git a/modoboa/extensions/amavis/__init__.py b/modoboa/extensions/amavis/__init__.py
index 2140863af..48de7c7ef 100644
--- a/modoboa/extensions/amavis/__init__.py
+++ b/modoboa/extensions/amavis/__init__.py
@@ -54,12 +54,15 @@ class Amavis(ModoExtension):
                                   help=ugettext_lazy("Mode used to access the PDP server"))
         parameters.register_admin("AM_PDP_HOST", type="string", 
                                   deflt="localhost", 
+                                  visible_if="AM_PDP_MODE=inet",
                                   help=ugettext_lazy("PDP server address (if inet mode)"))
         parameters.register_admin("AM_PDP_PORT", type="int", 
                                   deflt=9998, 
+                                  visible_if="AM_PDP_MODE=inet",
                                   help=ugettext_lazy("PDP server port (if inet mode)"))
         parameters.register_admin("AM_PDP_SOCKET", type="string", 
                                   deflt="/var/amavis/amavisd.sock",
+                                  visible_if="AM_PDP_MODE=unix",
                                   help=ugettext_lazy("Path to the PDP server socket (if unix mode)"))
         parameters.register_admin("CHECK_REQUESTS_INTERVAL", type="int",
                                   deflt=30,
diff --git a/modoboa/static/js/twocols_nav.js b/modoboa/static/js/twocols_nav.js
index 64e17b1b2..f15c487a6 100644
--- a/modoboa/static/js/twocols_nav.js
+++ b/modoboa/static/js/twocols_nav.js
@@ -37,7 +37,22 @@ TwocolsNav.prototype = {
         if (data.onload_cb) {
             eval(data.onload_cb + '()');
         }
+        $('#' + this.options.divid + ' select').change($.proxy(this.select_change, this));
         $(".help").popover().click(function(e) {e.preventDefault();});
+        $('#' + this.options.divid + ' select').change();
+    },
+
+    select_change: function(e) {
+        var $target = $(e.target);
+
+        $('div[data-visibility-field="' + $target.attr("id") + '"]').each(function(idx) {
+            var $this = $(this);
+            if ($this.attr("data-visibility-value") == $target.attr("value")) {
+                $this.show();
+            } else {
+                $this.hide();
+            }
+        });
     },
 
     save_cb: function(data) {