Dangerous Habits is a six-issue Hellblazer story arc written by Garth Ennis with art by Will Simpson, published by DC Comics, later under their Vertigo imprint.

The story features occult detective John Constantine contracting terminal lung cancer and attempting to con the Lords of Hell into curing it.

Dangerous Habits was written by Garth Ennis, who took over writing Hellblazer in 1991 after the conclusion of Jamie Delano's run on the series.

Upon hearing this, Constantine determines to cure it and save himself, knowing that his soul is damned and Hell is set to claim it upon his death.

However, each of the three Lords is too proud to simply cede John's soul to the others; surrendering a deal is seen as humiliating, and all three wish to uphold their reputations.

[5] Writer Jim Pascoe praised the comic, saying "The result is a tense supernatural drama that begins with Constantine being diagnosed with terminal lung cancer.

Though this book only hints at the freeform casualness and over-the-top vulgarity that became Ennis's trademark in the Preacher series, this is an immensely enjoyable read with strong characters and dynamite plot twists.

"[6] Dangerous Habits was voted the best Garth Ennis story on Comic Book Resources, ahead of his work on Preacher, The Boys and The Punisher.

[3] The popularity of Ennis and Dillon's run on Hellblazer is also credited for influencing Vertigo to agree to publish their seminal series Preacher.

Dangerous Habits also inspired the fifth season of Legends of Tomorrow, where Constantine's future death by lung cancer is advanced to the present by Astra, a girl he banished to Hell in a botched exorcism years ago, forcing Constantine to make a deal to extend his life by assuring Astra he will use the Loom of Fate to get her out.