According to Official Guinness Records,
The largest collection of tissue packs belongs to Silvio Fioravanti (Italy) and consists of 12,554 packs as of 31 May 2013, in Castelnuovo di Garfagnana, Lucca, Italy.
Silvio Fioravanti started his collection at the age of 15 in 1996. Currently, the collection consists of 12,554 unique packs from 78 countries.
For a complete list of 2013 records, please visit 2013 Guinness Records in Italy.