The Italian Seppi got past France's Eric Prodon in 6-1, 4-6, 6-1 fashion on the red clay at BNR Arenas.
The Day-2 upset came when Italian qualifier Alessandro Giannessi grounded the eighth-seeded Montanes 7-5, 6-4. The Spaniard Montanes titled here two years ago.
Veteran Romanian crowd favorite Victor Hanescu exited the draw when Spaniard Albert Ramos straight-setted him in 6-4, 6-3 fashion. Hanescu was the Bucharest runner-up back in 2007.
The host nation got wins from wild cards Adrian Ungur and Marius Copil, as Ungur handled Czech Lukas Rosol 6-4, 6-1, while Copil doused fellow Romanian wild card Victor Crivoi 6-3, 6-3.
Several other men posted first-round victories, including Italian Filippo Volandri, French qualifier Florent Serra and Russian Igor Andreev. The 2005 Bucharest champion Serra will meet top-seeded and defending titlist Juan Ignacio Chela in the round of 16 on Wednesday. The Argentine Chela beat Spaniard Pablo Andujar in last year's Bucharest finale.
The 2011 champion here will earn $93,000.