While the behavior of a software system can be easily changed by modifying the values of a couple of configuration options, finding one out of hundreds or thousands of available options is, unfortunately, a challenging task. Therefore, users often spend a considerable amount of time asking and searching around for the appropriate configuration options in online forums such as StackOverflow. In this paper, we propose ConfigMiner, an approach to automatically identify the appropriate option(s) to config-related user questions by mining already-answered config-related questions in online forums. Our evaluation on 2,062 config-related user questions for seven software systems shows that ConfigMiner can identify the appropriate option(s) for a median of 83% (up to 91%) of user questions within the top-20 recommended options, improving over state-of-the-art approaches by a median of 130%. Besides, ConfigMiner reports the relevant options at a median rank of 4, compared to a median of 16-20.5 as reported by the state-of-the-art approaches.