<ul id="combotree"></ul>

 $(function () {

        $("#combotree").combotree({

            width: 300,

            data: [{

                "id": 1,

                "text": "My Documents",

                "children": [{

                    "id": 11,

                    "text": "Photos",

                    "state": "closed",

                    "children": [{

                        "id": 111,

                        "text": "Friend"

                    }, {

                        "id": 112,

                        "text": "Wife"

                    }, {

                        "id": 113,

                        "text": "Company"

                    }]

                }, {

                    "id": 12,

                    "text": "Program Files",

                    "children": [{

                        "id": 121,

                        "text": "Intel"

                    }, {

                        "id": 122,

                        "text": "Java",

                        "attributes": {

                            "p1": "Custom Attribute1",

                            "p2": "Custom Attribute2"

                        }

                    }, {

                        "id": 123,

                        "text": "Microsoft Office"

                    }, {

                        "id": 124,

                        "text": "Games",

                        "checked": true

                    }]

                }, {

                    "id": 13,

                    "text": "index.html"

                }, {

                    "id": 14,

                    "text": "about.html"

                }, {

                    "id": 15,

                    "text": "welcome.html"

                }]

            }]

            ,

            method: 'get',

            ines: true,

            multiple: true,

            onBeforeCheck: function (node) {

                //alert($("#combotree").combotree("tree").tree('isLeaf', node.target));

                if (!$("#combotree").combotree("tree").tree('isLeaf', node.target)) {

                    return false;

                }

            }

        })

    })

onBeforeCheck: function (node) {

                //alert($("#combotree").combotree("tree").tree('isLeaf', node.target));

                if (!$("#combotree").combotree("tree").tree('isLeaf', node.target)) {

                    return false;

                }

            }