Onopka moved to the Ukraine capital, Kyiv, in 2001.
While there, she was spotted by a foreign scout and thus began her career as a model. In 2005, she appeared in campaigns for Dolce & Gabbana and Prada and caught the eye of Steven Meisel, who photographed her for two covers of Italian Vogue and for whom she is the current "muse."
Onopka has also been on the cover of i-D, Numéro, Harper's Bazaar, L'Officiel, Elle Ukraine, Akademia, CM, and the Portuguese, Japanese, and French editions of Vogue.
Although she missed New York's Fall/Winter 2007 fashion shows while shooting the Shiseido Spring/Summer 2007 campaign, she returned to the runway for the Milan shows weeks later, walking for Burberry, Jil Sander, Gucci, Dolce & Gabbana, and others.
Onopka is signed to the modeling agencies Women Management (New York), Viva Models (Paris) and Why Not Model Agency (Milan).
Onopka is one of the thinnest models walking the runways today, with a Body Mass Index of only 14.6 (anything under 18.5 is considered underweight) and thus faces rejection from some cities' Fashion Week shows, such as Madrid, which has a minimum BMI requirement.
Snejana only walked a couple shows for the Spring 2009 rtw and did not walk any spring couture shows.