In 1997, Moreno won the Pan American Junior Championships in Havana with a throw of 55.74 metres, improving the two-year-old championship record with ten metres. She beat the second-place finisher Maureen Griffin by a 46 centimetre margin. This year she threw past the 60 metre mark for the first time, with 61.96 m. The next year, she finished fourth at the 1998 World Junior Championships, this time 29 centimetres behind Griffin. After the World Junior Championships, Moreno started working with a new coach Eladio Hernández, himself a former hammer thrower. The cooperation paid off almost immediately as Moreno established a new world junior record on 29 May 1999 with 66.34 metres at altitude in Mexico City.