Hănescu earned his first ATP singles ranking points in August 1999, with first-round wins two weeks in a row at the Romania F1 and F2 Futures tournaments.
Although he played four more tournaments from September through December, he did not earn any additional points and finished the year ranked No.
Hănescu won his first pro tournaments in May 2001, taking the singles titles in consecutive weeks at the Slovakia F1 and F2 Futures events.
In July, as the top seed in consecutive weeks in Bucharest, he reached the final at Romania F1 and won the F2 Futures event to improve his ranking to No.
He broke into the top 200 for the first time in October, but went just 4–7 in Challengers after August and finished the year ranked No.
His highlights were reaching his first career ATP-level quarterfinal at Umag, Croatia in July, and then winning his first Challenger in Portugal in September.
At the end of May, he qualified for the French Open and reached the third round, losing to Jarkko Nieminen, to break into the top 100 for the first time.
He was ranked high enough for direct entry into all four Grand Slams and the Olympics but won only one match total in those five events.
His lone success was winning the ATP-level exhibition tournament in Houston in April, beating Vince Spadea and Juan Mónaco.
His ranking continued to plummet due mainly to inactivity, as well as poor results when he did play, until March, when he qualified for a Challenger event in Italy and beat No.
His protected ranking status gave him direct entry into a couple ATP events in April, with little success.
So he continued to play Challengers, reaching a semifinal and a quarterfinal in May, and then a final in June to get back into the top 300.
151 by the start of his home ATP stop in Bucharest in September, where he was a semifinalist in 2005; he went one step further this time by making the finals, losing in three sets to Gilles Simon.
In December, the ATP entered Hănescu into the 2007 Centuries Club for advancing hundreds of spaces to regain a spot in the top 100 rankings.
He reached the second round of the Australian Open, after defeating Jan Hernych, but then fell to Dudi Sela.
Then he played Nicolas Devilder and won 6–2, 6–3, 6–1, to advance in the third round, where he lost to eighth-seeded Gilles Simon 2–6, 5–7, 2–6.
At the 2009 MercedesCup, he reached the final by defeating Dominik Meffert, Rainer Schüttler, Alexandre Sidorenko, and Fabio Fognini in the semifinals.
At the 2010 Australian Open, he won his first-round match against Juan Ignacio Chela 6–4, 6–3, 7–6, but then lost in the second round to World No.
He then played at the 2010 BNP Paribas Open, where he won his first-round match against Juan Ignacio Chela 6–3, 7–6, and then lost again to Roger Federer 3–6, 7–6, 1–6.
7 and top seed Gaël Monfils at the MercedesCup, after saving two match points in the second-set tiebreaker.
He also went out in the second round in São Paulo to Nicolás Almagro, who had beaten him in the final in Nice the previous year.
He was defeated in the second round in Buenos Aires by upcoming Japanese star Kei Nishikori in three sets.
At the 2010 Wimbledon Championships, Hănescu was booed and taunted by a group of spectators during his third-round loss to Daniel Brands of Germany.
Frustrated due to the injury and crowd behavior, he responded by spitting toward some spectators and received a warning from the umpire.
[5] He then deliberately made four service foot faults to lose two points, giving Brands a 3–0 lead in the final set, before retiring.