1998 Tercera División play-offs
The 1998 Tercera División play-offs to Segunda División B from Tercera División were the final playoffs for the promotion from 1997–98 Tercera División to 1998–99 Segunda División B. The first four teams in each group took part in the play-off.
Format
The 68 participating teams were divided into 5 series each made up of 4 groups in the category, with the exception of Series E , which was only formed by Group XII . Each series was divided into 4 groups formed by a 1st, a 2nd, a 3rd and a 4th classified from each group, which played a double-round playoff. Each victory was equivalent to 3 points, the tie to 1 point and the defeat to 0 points. The champion of each group obtained the promotion to Second Division B.The distribution of each series was as follows:
Teams for 1997–98 Play-Offs
Group I – Galicia  | Group II – Asturias  | Group III – Cantabria  | Group IV – Basque Country  | Group V – Catalonia  |
| 1st SD Compostela B | 1st CD Lealtad | 1st CD Tropezón | 1st CD Basconia | 1st FC Barcelona C |
| 2nd CD Lalín | 2nd AD Universidad de Oviedo | 2nd SD Noja | 2nd Zalla UC | 2nd Palamós CF |
| 3rd RC Celta de Vigo B | 3rd Navia CF | 3rd UM Escobedo | 3rd Real Sociedad B | 3rd CE Mataró |
| 4th Betanzos CF | 4th Club Siero | 4th Castro FC | 4th SD Amorebieta | 4th CD Tortosa |
Group XI – Balearic Islands  | Group XII – Canary Islands  | Group XIII – Region of Murcia  | Group XIV – Extremadura  | Group XV – Navarre and La Rioja   |
| 1st CD Atlético Baleares | 1st Universidad LPGC CF | 1st Cartagonova CF | 1st Jerez CF | 1st CD Calahorra |
| 2nd CD Constancia | 2nd CD Corralejo | 2nd Águilas CF | 2nd Mérida Promesas UD | 2nd Peña Sport FC |
| 3rd CF Sporting Mahonés | 3rd UD Las Palmas B | 3rd Sangonera Atlético CF | 3rd SP Villafranca | 3rd CD Logroñés B |
| 4th CF Villafranca | 4th UD Lanzarote | 4th Caravaca CF | 4th CD Badajoz B | 4th CD Azcoyen |