Mr Smith, 43, originally from Daviot, Inverurie has been reported missing after failing to return home yesterday afternoon after going hill running in Perth and Kinross.
He has been described as an experienced fell runner and was expected back yesterday at 5pm. He went out to run Meall nan Aighean, Carn Mairg, Meall Garbh and Carn Gorm.
His cousin, Ruth McKee has said: "We're desperately worried about him. Chris is a brilliant runner and is totally experienced with training in this kind of challenging terrain but he
may have become disorientated and could be further afield than the Glen Lyon/ Loch Tay area.
"If everyone in the area could keep a look out for him or let us know if you have seen him it would mean so much to his whole family."
Ms McKee said that Tayside Mountain rescue launched their search this morning and have been joined by a coastguard helicopter.
She continued to say that Mr Smith has two brothers who live in Aberdeenshire and a sister who lives in Milngavie, who have all joined the search. She added that his
parents are currently driving over from their home in Belfast.
Ms McKee shared a flyer on her Twitter account which reads in part: “If you're in the Glen Lyon/Loch Tay area today, please keep a look out for Chris. Chris is an experienced fell runner and Dad to two boys who are missing him so much.”
Mr Smith now lives in Haywards Heath in Surrey with his wife and two young sons. He was visiting his sister and her family in Glasgow earlier this week before taking a short holiday with his wife and sons in Perthshire
A Police Scotland spokesperson said: "Officers in Perthshire and mountain rescue teams are carrying out searches in the Glenlyon area following a report of a missing 43-year-old
man. Chris Smith was last seen at around 3pm on Tuesday October 27.
“Emergency services are being assisted in the searches by the Coastguard helicopter. Anyone with information is urged to contact police on 101, quoting incident 2775 of 27 October."