Praise be to Allah.
The Qur’aan is the word of Allaah which was revealed to Muhammad (peace and blessings of Allaah be upon him). It is mustahabb to read it and recite it frequently. This is one of the means of raising one’s status in Paradise, as it was narrated in the hadeeth of ‘Abd-Allaah ibn ‘Amr ibn al-‘Aas (may Allaah be pleased with them both) that the Prophet (peace and blessings of Allaah be upon him) said: “It will be said to the companions of the Qur’aan (i.e., those who read it much), ‘Read and rise in status, recite as you used to recite in the world, for your status will be commensurate with the last aayah you read.’”
Likewise, listening to the Qur’aan is also mustahabb, as the Prophet (peace and blessings of Allaah be upon him) listened to the recitation of Abu Moosa al-Ash’ari, and he said to him, “If only you could have seen me when I was listening to your recitation yesterday.” And the Prophet (peace and blessings of Allaah be upon him) asked ‘Abd-Allaah ibn Mas’ood (may Allaah be pleased with him) to recite the Qur’aan to him. ‘Abd-Allaah said, “Should I recite it to you when it was revealed to you?” The Messenger (peace and blessings of Allaah be upon him) said, “I like to hear it from others.”
So your listening to the Qur’aan on CD, as you asked about, or from a tape recorder or on the radio or TV, comes under the same ruling (i.e., it is mustahabb), whether that is at home, in the car, on the bus or in any other appropriate place. So long as you focus on it and do not listen to it whilst doing something else, you will be rewarded for listening. And Allaah knows best.