Hi, I have some old backlinks with good PR. some of them are shown in the link: page of Google, while others not. Will they all pass PR to my site?
Not showing as a link doesn't mean it doesn't pass PR, and it doesn't mean it does. Google can block sites from passing PR and there is really no way to tell unless it is the only link you have. Don't worry about a link not showing as a backlink, google only shows a fraction of backlinks on purpose (to keep your competitors from trying to get the same backlinks).
Thanks (rep+ ), It sounds reasonable. Another question: why the non-relevant links are shown, but the relevant link can be found nowhere?
Google just shows a 'sample' of your backlink profile. It's not necessary that these are the 'best' backlinks to your site. I use webmaster tools to find my backlinks. It's much more reliable and let's me download links in a file.
I agree with the comments above about the link: command only showing a sample of backlinks. That sample is not necessarily your best links or your most relevant links. Since Google Webmaster Tools shows more backlinks, it can be assumed that the link: command links are usually not the only ones passing PR. Yahoo Site Explorer does show a greater sample of backlinks, but those include nofollow links and other links that Google may not give credit for. So it may be useful for finding links, but they might not help your Google rankings.
I find this tool is really good for giving you an idea of the PR that you are getting from each of your backlinks. It tells you the PR of the page your link is on and the PR of the homepage. It also says if it is dofollow or nofollow and tells you the anchor text and the number of links on the page. Hope this helps! http://seopro.com.au/free-seo-tools/link-checker/