Not necessarily to buy tickets online. You can get them at the ticket office in the church (which is also the meeting point and not the altar). The experience was interesting and worth seeing when in Naples. You also get an entry to the second Catacombs di San Gennaro as part of this ticket, which can be used within a year I was told by the tour guide, although this is not confirmed.

excellent experience never done roman catacombs tour before was really good and intresting guild tells u about the history what happened there and the graves there.the only down side u cant do videos inside but other than that really happy with the tour and if go to naples again will do it again for sure.

A very informative and interesting attraction. A real insight into the history of Neopolitan life. our guide was fantastic. Extremely enjoyable. We also received an entrance ticket for the St Gennaro Catacoombs valid for 12 months which was a nice gesture. Excellent.