Household deodorizers and moth repellents are common agents implicated in many childhood poisonings. Their ingredients usually include either paradichlorobenzene or naphthalene compressed into a solid ball or another shape, sometimes with added essential oils and fragrances. Because medically naphthalene is a more important toxin than paradichlorobenzene, with hematologic and nervous system effects, clinicians often seek to discern which product has been ingested. We discovered fortuitously that a mothball swallowed by a retarded adult was radiopaque, and so designed an in vitro experiment to study the radiopacity of a variety of household deodorizers and products. Of 10 products screened for radiopacity by two radiologists, those containing paradichlorobenzene were consistently strongly radiopaque; those containing naphthalene were radiolucent. A third alternative ingredient which is used in some toilet bowl deodorizers, cetrimonium bromide, was also radiopaque. Radiopacity of paradichlorobenzene or cetrimonium bromide-containing products did not dissipate with time. We speculate that the halogen within the chemical structure of these compounds accounts for their radiopacity. We conclude that paradichlorobenzene-containing commercial products can be distinguished clinically from those containing naphthalene by the performance of an abdominal radiograph.