The purpose of black comedy is to make light of serious and often taboo subject matter, and some comedians use it as a tool for exploring important issues, thus provoking discomfort and serious thought, as well as amusement, in their audience. Popular themes of the genre include rape, murder, suicide, war, terminal illness, abuse, insanity, disease and crime. By contrast, so-called blue comedy focuses more on crude topics, such as sex and bodily fluids.

Although the two are interrelated, black comedy is different from straightforward obscenity, in that it is more subtle and doesn't necessarily have an explicit intention to offend; black comedy should be contrasted with obscenity. In obscene humor, much of the humorous element comes from shock and revulsion, while black comedy usually includes an element of irony, or even fatalism.