Take the the blue line no. 11 on the subway from Stockholm Central towards Akalla.
Get of at Kista - aprox travel time 17 minutes.
From Kista Centrums Subway station there is a 12 minute walk to Kistamässan. Follow the signs towards Kistamässan.
The subway goes aprox 6 times per hour.
Take the commuter train from Stockholms Central towards Upplands Väsby or Märsta.
Get of at Helenelunds station - aprox travel time 12 minuter.
From Helenelunds station there is a 5 minute walkto Kistamässan. Follow the signs towards Kistamässan.
The commuter train goes 4-6 times per hour.
Several buses serve Kistamässan.
Time tables are availiable on sl.se