I have, for example, the next XPath query:
//div[span=\"something\"]/parent::div/child::div[@class=\\\"someClass\\\"]
I want to use this XP
jQuery only has limited support for XPath. You can see what it does support here: http://docs.jquery.com/DOM/Traversing/Selectors#XPath_Selectors
As mentioned by @Ameoo you can use the evaluate method, which is available in most modern browsers - except, predictably, IE: jquery select element by xpath