Francesco Bidognetti's dutiful daughter-in-law was also nabbed as part of the sting on the “Casalesi” clan, the most powerful wing of the Naples-based Camorra organized crime group, the police said.
All three women are accused of mafia association and extortion.
They are suspected not only of transmitting Bidognetti's orders to the clan but also of playing a key role in the syndicate, allocating funds to associates and providing financial help to those imprisoned.
Bidognetti's two daughters, aged 35 and 27, were picked up along with his daughter-in-law in Casal di Principe, north of Naples.
It is the fiefdom of the ruthless Casalesi, which has mown down at least 1,000 people in 30 years.
Police did not specify how many of the other arrests were warrants presented to criminals already behind bars, a common practice in Italy.
Bidognetti earned his stripes as the right-hand man to famed Casalesi chief Francesco “Sandokan” Schiavone, who was jailed in 1998 and immortalized in the bestselling novel and film “Gomorra” by investigative journalist Roberto Saviano.
Schiavone and his crew were involved in brutal score-settling between clans fighting for control of Casal di Principe in the 1980s and 90s as well as peddling illegal drugs.
Bidognetti fell with them and was also convicted of burying tonnes of highly toxic waste in the Naples region.
In January 2010 Italy's highest court upheld life sentences against 16 Casalesi members, including Bidognetti and Schiavone.
Writer Saviano, who lives under police protection, described the Casalesi as “a confederation” of mafia families formed of “violent business leaders, murderous managers, builders and landowners, each with his own armed band and all linked by economic interests in most sectors”.