Cannabis is widely smoked in Europe and its increasing use is becoming a major public health problem. Adulterating cannabis with glass beads or sand is a new trick used by dealers to increase the weight and boost profits. These recent practices are not without danger. We report two cases of respiratory symptoms related to the use of this kind of adulterated cannabis. The first case is a 33 year-old patient admitted for an acute inhalation pneumonitis secondary to smoking cannabis adulterated with grit sand. The CT scan showed patchy ground-glass opacities, mainly in the upper lobes. A broncho-alveolar lavage, examined under polarized light, revealed birefringent intracellular particles, identified as silica, in alveolar macrophages. Spontaneously clinical and radiological improvements were observed after stopping the use of contaminated cannabis. The second patient, who smoked cannabis mixed with glass beads, described epistaxis, mouth ulcers, sore throats and cough. CT scan and BAL were normal. Adulteration of cannabis with microscopic glass beads, alone or mixed with sand, is a recent and widespread practice in Europe. These anecdotal reports prompted the French Department of Health to advise cannabis smokers of the harmfulness of these contaminants.