The 32-year-old civil servant points to the glossy image of a bespectacled grinning face, with a thick beard and a turban.
"Who is this?" he asks his son, Zein.
"Hassan Nasrallah," comes the shy answer.
"And who is this?" Hussam asks, this time pointing to a second figure on the left-hand side of the same poster, also smiling, and separated from the Hezbollah leader by a bed of flowers.
Zein again replies correctly: "President Bashar."
Hussam pats his son on the head, hands over 10 Syrian pounds (about $0.20) to the bookseller, and leaves with the poster.
Symbols of resistance
Such posters – and dozens of variations - have become increasingly common sights in Damascus since Hezbollah captured two Israeli soldiers on 12 July, triggering the current war in Lebanon.
They adorn car windows and shop fronts, while yellow and green Hezbollah flags flutter from street corners, side by side with the Syrian flag or even its Lebanese counterpart.
For some Syrians, openly backing Hezbollah mirrors support for their own country's stance on the Lebanon crisis.
Bilal Mohamed, 25, who sells posters and books from his stall in Damascus's old city, says: "For me, both President Assad and Hassan Nasrallah represent the resistance."
As a close backer of Hezbollah, Syria has repeatedly been accused by Israel and the US of acting as a conduit for arms and supplies sent into Lebanon.
The Syrian government denies this charge, and, in contrast to the lukewarm endorsement which most other Arab governments have given Hezbollah, has been outspoken in its support for the Lebanese Shia group and its leader.
And the current conflict with Israel has boosted Nasrallah's popularity to that of a cult-like figure.
Hezbollah paraphernalia, long available in parts of Lebanon, now appear to be a growth industry in Syria, too.
Abou Radwan, an employee of the Al-Quds (Jerusalem) bookshop in a central Damascus market, says: "Ever since 2000 when Israel withdrew from south Lebanon, a few people have been asking me for Hezbollah flags or posters.
The Hezbollah logo on T-shirts
for sale in Damascus
"But since 12 July, people from all over Syria are coming here to buy pictures of Nasrallah and President Assad."
On many of the posters and postcards on sale, Nasrallah now appears as part of a trio with Bashar Assad, the current president, and his father, Hafez al-Assad, who ruled Syria from 1971 till his death in 2000.
Customers can also invest in a collage of the Shia leader's smiling face superimposed over a burning Israeli warship, cartoonish flames roaring from its side in a recreation of the Hezbollah 14 July missile attack which crippled the vessel.
"People come to me for my posters, because they have the highest resolution," says Abou Radwan, who sells hundreds of such images a day.
"A shop in Aleppo has tried to compete with me and print their own versions," he says, holding up an inferior-quality image of Nasrallah’s smiling face overlooking a crowd.
"But mine are better."
A people's hero
Hezbollah T-shirts, key rings and even CDs are being snapped up; bookshops are also selling a 352-page biography of the group's leader, published in Cairo and entitled The'ir min Jnoub, or The Revolutionary from the South.
"Lots of people want to know more about Nasrallah's life and times now," says Mohamed, working outside the Damascus citadel.
"He is the first leader since Saladin who will defend all the Arabs"
Rola Melli, 21 ,student
And for some of Syria's youth, the Lebanese Shia leader has become an inspiring reminder of their great historical heroes.
In a cafe near Bab Touma in the Christian quarter of the Old City, Rola Melli, a 21-year-old Sunni Muslim student, explains her support for Hezbollah.
"Nasrallah has become a hero for the Syrian young. For us, he represents Saladin," she says, referring to the 12th-century Muslim leader who defeated the Crusaders and retook Jerusalem.
Saladin is buried in Damascus.
"He is the first leader since Saladin who will defend all the Arabs, whether they are Shia or Sunni, Muslim or Christian, and he will bring us our dignity," she said.