Russia is hosting talks involving the Syrian government and some rival figures, but the main opposition group has stayed away, limiting the chance of any breakthrough towards ending the country's conflict.
Delegates said on Monday they expected the four-day meeting to focus on humanitarian issues, and the aim was largely to build confidence after four years of conflict that have killed more than 220,000 people in Syria.
The Western-backed Syrian National Coalition, based in Istanbul, boycotted the meeting, saying it would take part only if the talks led to the stepping down of Syrian President Bashar al-Assad, an ally of Russia.
Sergey Lavrov, Russia's foreign minister, said Moscow still hoped that agreements reached at talks in Geneva in June 2012 would be implemented and suggested the absence of one opposition group should not be overstated.
"So much blood has already been spilled in Syria and so many false starts have been made ... that we must not be guided by the fact that someone has declared one opposition group the main one and make this the basis for trying to achieve a result," Lavrov said.
A document drafted at the 2012 Geneva conference and approved by Washington and Moscow called for the creation of a transitional government body formed by mutual consent.
List of delegates
The Syrian government delegation in Moscow was headed by Bashar Jaafari, the country's ambassador to the United Nations, Russian news agency Interfax said.
It said the list of participants was similar to the line-up during a first round of consultations in Moscow in January, which produced no breakthrough.
More than 30 representatives of various groups attended the earlier meeting, most of them from groups that are tolerated by Assad or who agree that working with Damascus is necessary to combat the rise of the Islamic State of Iraq and the Levant (ISIL).
Russia says fighting "terrorism" in Syria should be the top priority now and has called on the opposition to work with Assad to that end.