Dialog box

Can anybody provide some code on how to create a SP JavaScript dialog box (modal dialog).

I tryed using the 2010 code, but gives a strange error.

var options =
    {
        url: pageToLoad,
        title: 'Snapshot',
        showClose: true,
        width: 700,
        height: 250,
        allowMaximize: false,
        dialogReturnValueCallback: NotifyCallBack
    };

    SP.UI.ModalDialog.showModalDialog(options);