"If there is one major contribution in my life that caused most of my hair loss it is poor finishing," Queiroz told reporters on Friday, pointing to his bald patch.
"In terms of attacking potential we've had problems since the start."
Portugal struggled in their first few World Cup qualifiers, goal-scoring problems meaning they needed a late surge to reach the finals in South Africa.
"In the away game against Denmark something almost unheard of occurred, we had 36 shots and scored just once," said Queiroz.
That goal, which earned a 1-1 draw against the eventual group winners, was scored by Brazilian-born forward Liedson on his debut after he had obtained Portuguese citizenship.
The Sporting striker was a valuable addition to the team, netting twice more as Portugal improved their scoring record later in qualifying with the wingers, midfielders and defenders all chipping in.
TALENTED FORWARDS
Scoring woes returned however in the win over China in a friendly in March, with Portugal's talented forwards tormenting the defence but converting only two of several chances.
Liedson is likely to be the first-choice striker, ahead of Werder Bremen's Hugo Almeida, when Portugal start their World Cup challenge against Ivory Coast on June 15 in a group that also includes North Korea and Brazil.
Queiroz said he expected wingers Cristiano Ronaldo and Nani, both of whom he coached in a previous spell as Alex Ferguson's assistant at Manchester United, to get on the scoresheet in South Africa.
"Nani has been fantastic in the last few months. His decision-making has improved a lot as has his finishing," the coach said.
Queiroz also said Ronaldo had silenced the doubters after moving from United to Real Madrid for a world record 80 million pounds last year.
"In terms of performances I hope he can improve even more," said the coach.
