Cardinals electing the new pope will be looking for a charismatic but tenacious man capable of re-uniting a fractious Catholic Church, stamping down on scandals and re-igniting faith among the young.
"First of all, we need a pope who knows how to speak to the world - beyond the Catholic world," said Andrea Tornielli, Vatican expert for La Stampa daily's Vatican Insider insert.
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"He needs to be open and understanding, not too inward-looking," he said.
It will not be an easy decision, said John Allen from the National Catholic Reporter in Rome.
"There are conservatives versus moderates, there is third world versus first world ... and insiders versus outsiders," he said.
Good communication skills are a key requisite for many Vatican watchers: favourites are Timothy Dolan, the 63-year old Archbishop of New York who is renowned for his humour and dynamism, and Brazil's Odilo Scherer, 63, who is praised for his open mind and is a keen tweeter.
After the academic language of Benedict's sermons, many are also looking for a warmer pope - which could be Vienna's Christoph Schoenborn, 68, admired for his pastoral touch and compared by some to the much-loved John Paul II.
The next pope "has to be able to speak the language of God in the language of men", said French cardinal Paul Poupard.
Young faithful in particular have repeatedly said that the 85-year old pope's decision to step down because of his age is a sign the church now needs a more youthful and flexible leader.
At 55, Luis Antonio Tagle from the Philippines is the church's second youngest cardinal: he is tipped for his dynamism and charisma, and is hugely popular in Asia. Brazil's Joao Braz de Aviz, a 65-year old known for his attempts to reach out to breakaway liberals, is also well-liked.
The German Pope's reign was overshadowed by a vast sex abuse scandal which reared its head time and again despite Benedict's efforts, and many will be looking for a new pope capable of slamming down on pedophile priests.
Their man may be Sean O'Malley from Boston - where the scandal first exploded a decade ago - who has worked hard to crack down on abusers and sold the archdiocese's palatial headquarters to raise money for victim settlements.
Others will hope the new pope will tackle internal divisions, bickering and jostling for power within the unruly Curia - the central government of the Catholic Church.
Argentina's Leonardo Sandri, a 69-year old born in Buenos Aires to Italian parents, is considered a possible contender to bridge divides, while supporters of Canada's Marc Ouellet, 67, say he would crack down on the wilful Curia.
Many observers are hoping for a more progressive pope who could tackle sensitive topics such as homosexuality, the use of condoms and clerical marriage, but cardinals willing to open up on all fronts are few and far between.
Ghana's Peter Turkson, 64, is noted for easing the rules on contraception, advocating condom use among married couples if one partner is infected with AIDS.
But his recent comments in an interview suggesting homosexuality may be part of the reason for the sex abuse scandals damaged his chances says some observers: so too did his decision to show a synod a video sensationalising Muslim immigration to Europe.
Those hoping the future pontiff will carry on Benedict's efforts to improve interreligious relations and increase dialogue with the secular world by reaching out to atheists may be backing one of two Italian contenders for pope.
Angelo Scola, the 72-year old Archbishop of Milan is a keen promoter of dialogue between Muslims and Christians, while Vatican culture minister Gianfranco Ravasi, 70, has set up a series of exchanges with non-believers.
